My best advice for new Directv installs would be to get the Oval dish even if you don't need if yet. It's should be a very small extra cost ($100 or less) and this will future proof the install until DTV changes the rules again
I have nothing against Dish, I think the quality and service of both is excellent, but I like the hardware choices and guide on Direct better (this might change soon). Voom might be a good option in a year or two, if they last and if they can work the bugs out of the system (seems everyone right now is paying to beta test). The major difference right now between DTV and Dish on the HD side is the DVR functionality. Dish has theirs on the market already (I hear it's pretty buggy, but they will fix the software), I think it has two Dish tuners (a first for Dish, so you can watch something else while you record) but only one ATSC (OTA) tuner...the soon to be introduced DTV HD Tivo's will have 4 tuners: 2 each type, so you can record and watch different programming of either type at the same time. I hope this makes sense???