If 4-5 feet is going make or break it I don't think you'll know before you get there that the shorter setup would make it. Also, having towed both and of the lengths you're looking at, when going to remote places you're just as likely to get stuck by the 5th hitting your bed rails as you are due to length.
Honestly, I'd take my chances with a TT anyday over a 5th given the sharp changes in level you're likely to encounter. I had better than average clearance with my 5th (around 7" I think) and it was a close call pulling into my driveway with a mild slope. I can't imagine trying to haul it out boondocking on bumpy/uneven roads.
It's an interesting topic and I'm curious to hear what other say but I think overall a TT is much more capable than a 5th on rough/uneven roads.