Direct or Dish is personal opinion, and there are fans (and critics) of both. We have had Dish both at home and in the RV for many many years and happy with it. Dish does have a monthly plan you can start and stop whenever you want. Check dishformyrv.com for info.
I would go with a portable satellite antenna. For one it is cheaper than having one permanently installed on the roof. And two, if there are a lot of trees around it can usually be positioned to find a hole thru the trees to find the sats, something not so easy for a roof mount.