I own both and wheel with guys with both. Much of the answer really depends on what you plan on using the vehicle for.
I love my FJC and wheel the crap out of it. Yet, I think the 80 series has more potential (live front axle) in a couple arenas. Not that the FJC can't "keep up", just that the 80 is a tried and true workhorse. I drove my FJC from NC to CA to do Rubithon in '08 with my daughters and dog, hit Moab and Ouray on the way home w/o any issues. That trip alone impressed me like no other vehicle I've owned.
I'd agree with 1911 that the rear cargo area is larger in the 80 (not by a lot) as well as Gumby that it is a negative how the seats fold down in the FJC. Yet, I don't utilize my FJC much with the seats down so its really not an issue for me, though it might be for you. Yes, the suicide doors can be a pain if you have kids, someone needs to close the door for the rear occupants unless they learn how to do the seatbelt catch/close technique.
The biggest difference is overall visibility. In the 80, I feel like I'm driving the Popemobile where the FJC is driving in a much more "closed" vehicle. My daughters drive the 80 and I'm happy to put them in a 6klb vehicle with ABS and airbags, great vehicle for teenagers. Yet, still not the best daily driver as compared to the FJC IMHO.
Tough call, with more specific goals/plans for either vehicle, tough to give too much guidance...