The 80 is a great machine. The problem with the 6cyl 1993+ is that there is a known headgasket issue with a non-trivial amount of them. It was IMO a design flaw in the gasket itself. Once fixed is a non-issue (as currently known). If you are looking at an 80, look for seeping coolant between head and block in the later years; it's no big issue if you see it, just adjust price accordingly and get it done. It's live front axle but it drives like a dream. 91-92 FJ80s are the bastard LandCruiser children but in my opinion are well worth the effort to look at the right one.
The 100 is a very refined machine. The V8 is powerful and suprisingly does well in the heavy beast. It does not have the steep torque curve nor apex at a low enough RPM in my opinion for being a full-time trail rig; I'd prefer the 80 for that. The 100 is more highway friendly though, and has rear AC! It is IFS. I'll let you guess where Toyota decided to mount the starter on the V8. There's a known exhaust manifold cracking issue, listen for a ticking noise during a cold start.
You can't go wrong with either. We have both and love both.