Last Friday I bought the USDigital DB-2010 HDTV receiver from WalMart for $198.76. I was quickly impressed with its ease of use and the features it offered for such a relatively low price. But then I found the Samsung SIR-T451 HDTV receiver at Circuit City for $249.99 and was intrigued. I took one of these home last night to try out. Now I feel compelled to submit this mini-review comparing both receivers. Caveat lector, however, I only have SD sets so there are no picture quality comparisons...
The USDigital box is actually made by Hisense, a company in China. On the front are the power button, IR sensor, a CA card slot (for USDigital's service, see usdigitalhdtv.com), a 'signal lock' LED, and a power/standby LED. The signal lock LED is red when there's not a good enough digital signal coming in, green otherwise. The power LED is red when the unit is in standby and green when the unit is on. On the back are an antenna input, USB connection (for future use, as mentioned in the manual), optical digital audio output, component video output, composite video and S-Video outputs, and analog stereo audio output. There is no DVI connector on this box. The remote control has a nice layout with very ample functionality. The menus are somewhat plain looking, and are displayed over a blue centered background that covers most of the screen.
The Samsung receiver has more on its front panel than the USDigital. There are the power button, standby indicator, 'HDTV' signal indicator, tuned channel number display, exit button, menu button, enter button, and four-direction arrow pad. The HDTV signal indicator merely functions as a DTV signal lock indicator (not just for HDTV signals). The back of the box also has more connections than found on the USDigital. There are: antenna/cable input, antenna output, optical and coax digital audio outputs, composite video and S-Video outputs, two sets of analog stereo audio outputs, component video output, DVI video output, RGB 15-pin video output, a DTV output selector switch, and an output resolution selector switch. The antenna output only seems to be a pass-through of the antenna. The only mention I found of it in the manual is its label, "ANT. OUT" with no description. The remote control also has a nice layout with ample functionality. The menus are nicer looking, with icons, and on a smaller semi-transparent background.
From above, on the outside I definitely liked the Samsung (S* hereafter) more than the USDigital (U* hereafter). While I prefer optical over coax for digital audio, any box that outputs both is a bonus for me. The S* box can also be operated via front-panel, which U* lacks. I also like the RGB output on the S* for PC monitors, etc. I have a 21" Viewsonic right by my home theater 'command center' but never got around to trying it out. One superficial bonus for the U*, however, is its remote, which I felt is better ergonomically designed (general shape, button positioning, size, shape, etc.).
Now for some operational differences between the USDigital (U*) and Samsung (S*) receivers.
Channel flipping: the U* wins here, moving from one channel to another much quicker than the S*. Also, you can go to a specific subchannel on the U* while you can't on the S* (at least I never found a way). Example, to get to 16-5 on U* you press 1, 6, right arrow, 5, enter. On the S* you press 1, 6, and it automatically goes to your first subchannel on 16. Then you have to channel-up several times, waiting for each to come up.
Signal strength indicator: the S* annoyed me here, requiring me to navigate the menu to see the signal strength for the current signal. It displays strength as a dozen or so vertical bars of increasing length (like some mobile phones). On the U*, however, signal strength is part of the channel-changing (and Info button) OSD, which is nice. Much easier to get to.
OSD (via changing channels and Info button): the S* shows many little details about the current broadcast such as CC availability and selection, HD vs. SD, language availability and selection, etc. It also shows the brief program info. The U* shows slightly less details but is far less cluttered in my opinion--just a rectangle in the lower 1/4 of the screen. One last note, the U* OSD goes away after a few seconds like any normal receiver, but at any time afterward if you press the Info button it will stay on as long as you want it to, even while changing channels. This is a nice touch if you want to quickly compare your different channels' signal strengths.
Channel guide: the U* channel guide is quicker to navigate and less complicated. However, it blocks most of the screen (like its menus), while S* shows picture-in-graphic of the current channel in the corner.
Digital audio support: the S* has the option to select either Dolby Digital or PCM output. My audio receiver supports both, so I would just leave it on DD. The U* apparently only outputs DD.
Aspect compensation: this was a real showstopper on the S* for me. To watch 4:3 programming on a 16:9 screen (or the other way around), without stretching, the receivers will put panels on the left and right (or top and bottom). The U* puts black panels which works very well for me. The S*, though, uses a grey color for its panels. I'm not sure if that's for any ergonomic (eye strain, etc.) reason, or whatever, but it surely bugs the hell out of me. I could not find any way to switch those to black. Furthermore, the zoom function on the S* zooms in too far, cutting off the edges of a 4:3 picture (and a significant loss on the left and right sides). This of course could have been a setting problem on my end, but I did have the resolution/output selection switches on the back and the menu-based aspect ratio set right as far as I know. The U* zooms the 4:3 programming without any noticable cropping.
Tuner: both seemed to bring in about the same signal strength. I believe my U* is not one of the reported newer ones with a 5th generation tuner chip. I don't know what generation the S* has. Also, collectively, I don't know how these compare to other DTV receivers. On a related note, the S* supposedly has QAM support for unencrypted digital cable signals. I briefly tried the box on our Time Warner system, and while it found several subchannel numbers for channels 90 and 100, there was no signal nor any channel information (ID, etc.).
Front panel channel display: the U* is missing this handy feature. The S* displays on the front panel an 'A' followed by the channel number for OTA reception, and 'C' followed by the channel number for unencrypted digital cable reception. The display only shows the 'major' channel number; it is missing the subchannel. However, this display is an illuminated 7-segment LCD through a 'mirror'-like panel, which is cool.
That's all I can think of to compare at the moment. I apologize for my bias above toward the USDigital, but that is obviously the one I chose to stay with. I neglected to mention that it is most obviously running Linux inside
and when I saw that (at the very start), I basically fell in love with the box. 
The USDigital box is actually made by Hisense, a company in China. On the front are the power button, IR sensor, a CA card slot (for USDigital's service, see usdigitalhdtv.com), a 'signal lock' LED, and a power/standby LED. The signal lock LED is red when there's not a good enough digital signal coming in, green otherwise. The power LED is red when the unit is in standby and green when the unit is on. On the back are an antenna input, USB connection (for future use, as mentioned in the manual), optical digital audio output, component video output, composite video and S-Video outputs, and analog stereo audio output. There is no DVI connector on this box. The remote control has a nice layout with very ample functionality. The menus are somewhat plain looking, and are displayed over a blue centered background that covers most of the screen.
The Samsung receiver has more on its front panel than the USDigital. There are the power button, standby indicator, 'HDTV' signal indicator, tuned channel number display, exit button, menu button, enter button, and four-direction arrow pad. The HDTV signal indicator merely functions as a DTV signal lock indicator (not just for HDTV signals). The back of the box also has more connections than found on the USDigital. There are: antenna/cable input, antenna output, optical and coax digital audio outputs, composite video and S-Video outputs, two sets of analog stereo audio outputs, component video output, DVI video output, RGB 15-pin video output, a DTV output selector switch, and an output resolution selector switch. The antenna output only seems to be a pass-through of the antenna. The only mention I found of it in the manual is its label, "ANT. OUT" with no description. The remote control also has a nice layout with ample functionality. The menus are nicer looking, with icons, and on a smaller semi-transparent background.
From above, on the outside I definitely liked the Samsung (S* hereafter) more than the USDigital (U* hereafter). While I prefer optical over coax for digital audio, any box that outputs both is a bonus for me. The S* box can also be operated via front-panel, which U* lacks. I also like the RGB output on the S* for PC monitors, etc. I have a 21" Viewsonic right by my home theater 'command center' but never got around to trying it out. One superficial bonus for the U*, however, is its remote, which I felt is better ergonomically designed (general shape, button positioning, size, shape, etc.).
Now for some operational differences between the USDigital (U*) and Samsung (S*) receivers.
Channel flipping: the U* wins here, moving from one channel to another much quicker than the S*. Also, you can go to a specific subchannel on the U* while you can't on the S* (at least I never found a way). Example, to get to 16-5 on U* you press 1, 6, right arrow, 5, enter. On the S* you press 1, 6, and it automatically goes to your first subchannel on 16. Then you have to channel-up several times, waiting for each to come up.
Signal strength indicator: the S* annoyed me here, requiring me to navigate the menu to see the signal strength for the current signal. It displays strength as a dozen or so vertical bars of increasing length (like some mobile phones). On the U*, however, signal strength is part of the channel-changing (and Info button) OSD, which is nice. Much easier to get to.
OSD (via changing channels and Info button): the S* shows many little details about the current broadcast such as CC availability and selection, HD vs. SD, language availability and selection, etc. It also shows the brief program info. The U* shows slightly less details but is far less cluttered in my opinion--just a rectangle in the lower 1/4 of the screen. One last note, the U* OSD goes away after a few seconds like any normal receiver, but at any time afterward if you press the Info button it will stay on as long as you want it to, even while changing channels. This is a nice touch if you want to quickly compare your different channels' signal strengths.
Channel guide: the U* channel guide is quicker to navigate and less complicated. However, it blocks most of the screen (like its menus), while S* shows picture-in-graphic of the current channel in the corner.
Digital audio support: the S* has the option to select either Dolby Digital or PCM output. My audio receiver supports both, so I would just leave it on DD. The U* apparently only outputs DD.
Aspect compensation: this was a real showstopper on the S* for me. To watch 4:3 programming on a 16:9 screen (or the other way around), without stretching, the receivers will put panels on the left and right (or top and bottom). The U* puts black panels which works very well for me. The S*, though, uses a grey color for its panels. I'm not sure if that's for any ergonomic (eye strain, etc.) reason, or whatever, but it surely bugs the hell out of me. I could not find any way to switch those to black. Furthermore, the zoom function on the S* zooms in too far, cutting off the edges of a 4:3 picture (and a significant loss on the left and right sides). This of course could have been a setting problem on my end, but I did have the resolution/output selection switches on the back and the menu-based aspect ratio set right as far as I know. The U* zooms the 4:3 programming without any noticable cropping.
Tuner: both seemed to bring in about the same signal strength. I believe my U* is not one of the reported newer ones with a 5th generation tuner chip. I don't know what generation the S* has. Also, collectively, I don't know how these compare to other DTV receivers. On a related note, the S* supposedly has QAM support for unencrypted digital cable signals. I briefly tried the box on our Time Warner system, and while it found several subchannel numbers for channels 90 and 100, there was no signal nor any channel information (ID, etc.).
Front panel channel display: the U* is missing this handy feature. The S* displays on the front panel an 'A' followed by the channel number for OTA reception, and 'C' followed by the channel number for unencrypted digital cable reception. The display only shows the 'major' channel number; it is missing the subchannel. However, this display is an illuminated 7-segment LCD through a 'mirror'-like panel, which is cool.
That's all I can think of to compare at the moment. I apologize for my bias above toward the USDigital, but that is obviously the one I chose to stay with. I neglected to mention that it is most obviously running Linux inside
and when I saw that (at the very start), I basically fell in love with the box. 
