For TV service, I'd say compare the lineups from Comcast and Dish, then make your choice. If you like american sports, chances are you will be better off with Comcast than with Dish, because Dish will at best carry your Local RSN in HD for games only, whereas Comcast will probably carry it/them 24x7 in HD. Now, if you like soccer, then you really would need to check the Comcast lineup in your area, because Comcast carries Fox Soccer in HD in very few areas but, on the other hand, Dish doesn't carry Goltv at all while Comcast does carry it in SD.
For other HD channels, you are just better off comparing the 2 lineups. The challenge with Cable is that there are Comcast-serviced areas with close to 150 channels and others with a bit over 30.
As far as equipment goes, I had been a subscriber of the 3 providers. Nothing beats the 722k Dish box, however, the last Comcast box I have ever used was a 160Gb Moto 3416 box and, as some have stated here, Comcast has deployed newer DVR box.
In any event, if you are a sports fan, you probably will be a bit disappointed anyways, because only on Directv you have all these special channels for the big Tennis and Golf tourneys, the Sunday Ticket, the special channels for Uefa Champions League, Nascar Hot pass, etc.