I just sold my 80 to buy a 100 series.
Here are my reasons.
First off, i absolutely LOVE my 80 and think it is the best bang for the buck 4x4 made, PERIOD!
Main reason is POWER. The 80 lacks the ability to tow anything when modified for serious overland use.
I am shifting my priorities a bit and need something that can tow a car hauler and a car on a somewhat regular basis. My 80 simply would not cut it at its current state with all the mods.
I plan on finding a clean 98-99 100 series, doing some much lighter duty mods, and having a double duty rig as an overlanding vehicle and a tow rig.
The 80 is already somewhat underpowered, but add a tent, bumpers, winch, sliders, fridge, etc.... and the already sluggish 80 isnt going to be up for the task of towing anything bigger then an Adventure Trailer (or similar). Sure, modifications can be made such as gearing and tranny coolers and such, but either way, its overstressing the powerplant.
My 80 has brought me to some amazing far-a-way places that i wouldnt have been able to get to without it and i will definitely miss it, but i am looking forward to "moving on"
Either way, you cant go wrong, but as others have said, the 80 is geared to more serious wheeling, where as the 100 is the perfect candidate for a more "overland oriented" use!
My .02
Carry On!