As someone who has just switched from DirecTV, I can firmly say that Dish's HD PQ is on par with DirecTV. Neither one is better than the other. However SD on Dish is far superior than that on DirecTV. I am pointed to the eastern arc if that matters.
I agree with you that the SD quality is much better than DirecTV. Some SD channels on DirecTV looked almost like YouTube feeds.
HD seems to be about the same for me, except I think that my locals may have been a bit sharper on DirecTV. The 722K is worth the switch though, and I am looking foreward to the 922.