True, but Dish's 1080i is broadcast with only 1440 pixels in the horizontal direction, even for locals, and then scaled to 1920 in the receiver. Still though, even w/low bitrates, the MPEG-4 H.264 implementation is good enough that PQ differences between Dish and OTA are hard to spot. At least that's what I see with SF locals.
The biggest thing I notice between DISH HD and OTA is that OTA I get all but one of my digital channels and DISH only carries 2 of the majors and none of the minors. ABC & NBC and that's it. CBS & Fox are in retrans disputes as hard as that may be to believe. Otherwise I can't tell the difference.