Oddly, I can be helpful here... I went from a 2013 2 door JK to a '92 FJ80 late last year. I wanted more space and didn't feel like spending the insane money for a JKU.
I did know about the significant differences between 91-92s and 93+ 80 Series, but I found a 92 for a good price with low mileage that had everything I wanted--lockers, sliders, winch, etc. Is in great shape and had been well taken-care of by previous owners. That helped, as a lot of the baseline work had already been done. That said, I've put some money and elbow grease into it in my short period of ownership thus far.
My thoughts: this is a big, roomy, and heavy truck. I like the space because I camp a lot and have 2 big dogs who took up the entire 'trunk' of my JK. It's a satisfying vehicle to drive and in some ways, rides better than my JK. That said, it's not a modern vehicle. No airbags, no ABS, and terrible gas mileage. I averaged 12-14 mpg on my 1500 mile trip to drive the truck home, and now get about 8-9 mpg in the dead of winter on short drives around town. That hurts, even coming from a JK on 35s that got 13mpg around town. Even so, I'd have to drive a hell of a lot to spend more than I had been spending before on my Jeep payments when I had them.
Power is lacking. I can't speak for the FZE, but the 3FE is basically a fast tractor. (At least it's faster than my land Rover.) It has loads of torque, which is great off road, but you'll feel the power shortage on long uphill climbs on the highway. The truck goes 0-60 eventually, even if you floor it. I drove my JK like a sports car. My wife has a newer V6 Cherokee and the thing feels like a Lamborghini compared to the FJ80. But, I'm more of a slow 4x4 kind of guy. The FJ80 kills it in the snow. Again, it's a big, heavy truck.
Long story short, the two are very different trucks, and I'll echo everyone who said that you need to remember you're going back 20+ years in time to get into an 80 Series. Make sure you're handy and don't mind turning a wrench. These trucks will last forever if you're good about PM and don't neglect little problems. I've been pretty happy with mine despite all the differences. If you're looking for a go-anywhere truck that will still be running after the nuclear apocalypse, a Land Cruiser is for you. But if you're looking for something with as many features and creature comforts as your JK that gets great gas mileage, expect to be let down.
