Dish has room, but they seem to want to put other channels up instead. One can see Dish's strategy to just put the games up in HD on the RSNs instead of running them all the time to have room for other channels.
DIRECTV is being a touch disengenuous here too, you cannot get the out of market pro games on your RSN unless you buy a package like season ticket, so for non ticket subs it is 1 channel, not 25 like they make it seem.
As usual the consumer needs to look at what is provided by both providers and match the channels to their viewing needs/wants. Then pick the best provider/package. If you want HD sports DIRECTV tends to have more, if you want movies in HD, Dish is the answer.