DirecTV will have locals in HD long before Dish, probably by late 06 or early 07.
Comcast does not carry all the local digital stations, only the HD ones and still not KMPH, which has been HD for months now. You will be better off with an antenna as far as local digital reception than with Comcast. Note that although only 4 of our locals are doing HD, all the rest except for 49, the Catholic Channel, are doing SD digital. SD digital ota beats the crap out of Dish's analog locals as well as the Comcast analog feeds.
Comcast does not carry local analog channels digitally, it's still a crappy analog signal all the way to your house.