I have Direct TV.. I am not advertising for them however I researched and found this out. There is a "footprint" that the satellites beam towards the USA. They beam it towards the center thus as you reach the out edges the signal gets weaker. When you get higher in latitude towards canada or Alaska the footprint becomes very weak. Since the satellite is in geosynchronous orbit it puts the dish you are using pointing low towards the horizon instead up towards the sky. Remember the horizon is now towards the equator in Alaska or Upper Canada.
From what I have read here and other sites you can get a signal from time to time is there are no mountains or other objects blocking the signal from reaching your antenna. With all that said I believe in KISS theory and try to keep my RV simple in the electronics arena. What I mean by that is the less the better it will probably work. Your goal is TV and yes we all want HD and all the bells and whistles but we have to be realistic. Your lucky to get a signal at all much less HD.
I have DTV as previously stated. They tried to get me to give up my 4 individual boxes and go with the HD all around GENIE system. Its cheaper and I almost did until I realized I carry a room box with me sometime two. With the GENIE system you cannot take a box from one of the bedrooms or office. I opted with the older system. DTV stated I could rent a box by activating it and deactivating it and only paying for the days used.. Bah too much trouble and too much hassle.
One last item, we purchased a Winegard portable DTV dish that is automatic. All I do is set it in the area where it has a decent look at the southern sky and before I can walk back to the RV its locked on the satellite. I dont have to worry about inclination or degrees or skew. All done in seconds.
In retrospect, I would guess the footprint of DTV or Dish to be about the same so the provider would be up to you. I think either will do what you want but remember KISS when traveling.