I have been an installer for 15 years, working for a specialized, local, family owned, company. We have installed both Dish and DTV since 2001. I love Dish, the Hopper is awesome. I could go home and install DTV in my house any time I want, but I have no desire to do so. Dish's equipment is better and their prices are lower.
That being said, I have seen a lot in 15 years, countless installs and systems, and I can state unequivocally that DTV HD is slightly sharper. We have 2 side by side identical flat panels with Dish and DTV hooked to them in the office. My boss (the owner) is a Dish fan also, but he got DTV at home for 2 years just to give it a try. The first thing he noticed when he hooked it up to his high end TV's/projectors was that it was sharper, his wife mentioned the same thing. He did get rid of it and go back to Dish as soon as the 2 years was up, the Dish user experience is just much better.
But, the difference isn't huge, and I wouldn't use it as a reason to switch. I would personally recommend 2 Hoppers, or Hopper & Super Joey.