depends on which runner. the 2nd gen 90-95 is much smaller than the 80. the 3rd gen 96-02 is marginally smaller. about 4 inches all the way around. noticeable at first, but then it wears off. i had a 97 runner, pretty built with fr/rr lockers, sliders the whole 9. the locked ifs did surprisingly well, and helped me go anywhere more capable trucks were going save for obstacles where rollovers and severe body damage was imminent.
my old runner on 35's with a friends LX450 lifted on 33's:
think of the 80 as a marginally bigger but much heavier version of the 3rd gen. it is very tank like as the AWD makes it feel that much more robust. both very capable off road equally setup. neither arent powerhouses, but power to weight ratio, the 4runner wins purely based on weight and size. the 3.4L 5VZE was adequate. with any truck with bigger tires...lower gears are your friend. if you're smart, locked IFS shouldnt be a problem. size in the trails shouldnt be
much different. pin striping will happen on both trucks. 2" on each side wont make a difference. FWIW, 80s were available with front and rear lockers where the 4runner was available with rear lockers only.
i stepped up to the 80 as fitting 3 kids in the 4runner just didnt work. i can fit 3 wide in the 2nd row easily in the 80, the 3rd row just makes it that much easier. if you have lots of people to haul, go for the 80. if its just yourself and SO etc..the runner works fine.
cant go wrong with either or. if you plan on wheeling it...which ever one you choose...GET ONE WITH LOCKERS!