As toedtoes mentioned, a B+ is just a marketing term for a class C that does not have a cabover bed, basically speaking. Don't make anything of the distinction.
Any motorhome making a U-turn on a rural road with a trailer is going to be rather tough, doubly so for an inexperienced driver. If it were me, I would feel much better having them come get you in their car and then driving the rig and trailer there myself, even if it takes more time and gas and effort. I'd feel the same way if I were the one coming to pick up, as well. (I realize that this does have logistical difficulties with leaving the expensive aircraft unattended...it might not be a practical solution.)
For general driving, I don't tend to think that length makes a huge difference. I notice the height and width of my 32' class C much more than the length. Likewise, it doesn't have a huge impact on gas milage. The length does, of course, make a difference when maneuvering in tight areas. The turning radius of pretty much any class C is going to be rather horrid at best, and longer wheelbases do generally have worse turning radiuses. However, a short wheelbase relative to the overall vehicle has its own problems that are arguably worse: it often leads to poor stability on the highway, particularly when there are side winds or when towing, and magnifies the amount of tail swing when turning. (When turning sharply to one side, the back end of a class C will actually swing a good bit to the opposite side. If you're right next to a car or a fence or a building, it's not hard to accidentally collide with it when turning away from it if you aren't paying attention.)
In terms of reliability, the chassis of most class C's is easily the most reliable part. I would not worry about whether a Ford or Chevy chassis is still under warranty or not. If reasonable maintenance is performed, it should easily outlast the rest of the motorhome. Problems tend to more often crop up in the various appliances and systems of the house part of the motorhome, and in keeping the water on the outside and in the tanks/pipes and not elsewhere. Most any used RV is not going to have a comprehensive warranty on these parts, though some of the appliances etc. may still be under their respective manufacturer's warranties.
For five days off the grid, you pretty much need a generator, and might be well served by having a decent solar setup and a relatively large battery bank. Given that, your limiting factor will likely be fresh water and gray water tank sizes. Water conservation practices do play a big role there, of course. If you have a dump station and water fill spigot available, that makes things a lot simpler.