Sounds as if you might be looking at Scamps or Casitas, considering the sizes and weights you propose. Did I guess correctly? :)
The longer trailer punches just about the same hole in the air as the shorter one, so you shouldn't have any difficulty with either one. The 3.6L V6 has enough power to do the job. With the old 5-speed auto, you probably have an overdrive lockout that you'll want to engage while towing to avoid excessive torque converter heat in the tranny.
Backing either trailer is a matter of practice. The shorter one will swing to the side a tad faster than the longer trailer, but not a huge difference.
As for boondocking, size is not much of an issue. But if your fresh water tank is small, you may need to carry extra water (jerry cans work well) depending on how long you want to be in one spot. Pay attention to ground clearance if you plan to boondock along rough forest roads.