I bought a King Flex, the "Super Tailgater". It receives DirecTV SD, Dish SD and HD and Bell. Another difference is the Flex has a connection for a second TV. Last month we switched from DirecTV to Dish at the house. I negotiated to get two ViP211k receivers directly from Dish (not through a reseller) for $49 each. It costs $7 a month for service per ViP211. For me the difference is the ability to have HD in the RV and not to struggle manually aiming the DirecTV dish for HD. We have found the picture quality from Dish to be noticeably better at home on the big TV. My wife, not a video expert, made that observation. Also, the Hopper with Sling is fantastic! I loved the DirecTV Genie and thought it was tops but, boy, was I wrong. In the RV I was able to connect the over the air antenna to one of the receivers so I can integrate the OTA locals into the Dish program guide. For $45 Dish will unlock the DVR capabilities of the ViP211 so you can add an externally powered hard drive to record your favorite programs.
Both DirecTV and Dish have pros and cons but if you are like me and want HD in the RV at the easiest, lowest cost, Dish is it.