I have both. The ride quality and perceptible power between the 100 and the 80 is huge. If you can afford a 100, get it, if a 200 is affordable then get that, because it
IS that much better.
If you are going to be doing really serious rock crawling, the 80 is better only because of the solid front axle that
may keep both front tires in contact with the ground (depending on the situation). Also, you will be able to build a really nice 80 for what you would pay to enter the 100 (but it will never ride as well nor have the amenities of the 100).
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It's predictable that you will always have the guys who say their vehicle was that last model of the "real" (insert manufacturer name here). I've heard 60 guys will say that the 80 isn't a "real" cruiser, what a bunch of crap, even more, the 40 guys will say the 60 isn't a real LC. Don't pay attention to it, stay focused on what you are looking for in the vehicle.
The 100 is noticeably larger inside and has side airbags, so if you were planning on a family and having the rig for some time, the 100 may make better sense. My passengers prefer the 100 hands down - its more comfortable with the rear air-conditioning, the heated seats, better ride, lower noise level, more room, more comfortable seats and heated seats and all without the hot passenger side floor boards of the 80. As a driver, I prefer the 100 because of the better steering, handling, braking , cooling (engine and cabin), transmission and power. It's wider than the 80 if you were to remove the fender flares on the 80. I really love both my Cruisers but if I could only keep one, the 100 works best overall for my needs and wants.
[The fact is the Land Cruiser is a purpose built, well engineered vehicle, period. Overall, the 80 is better than the 60, the 100 is better than the 80 and 200 is even better than the 100, like it or not. Now, with all that said, I want a 40 next because they're damn cool.