I thought I'd chime in quick here as I went through the exact same decision process roughly 2 months ago and picked up a 2001 Gen II Montero Limited with 95k a couple weekends ago. (Got tired of waiting for a good Gen II +2003)
We were looking at a GX470 or a Gen II Montero and test drove several GX470s before a reasonable Montero came up. The biggest difference I found between them was the overall approach to building a vehicle - the GX470 was a "nice" SUV, and the Montero was a "useful" SUV. A great example is the difference in rear suspension, the GX has airbags, which are very comfortable (when working), and easy to adjust for towing - however, if they break on the trail you're hosed, and furthermore, they're wicked expensive to fix. Sure you could upgrade to a GX with KDSS (if you could find one) and it's better, but again, when they break replacement costs start at 2k and go up from there, or you could do a spring replacement. On the otherhand, Montero went with a substantially lower tech approach (shocks and coil springs) that is way more robust, cheaper, and less likely to fail catastrophically.
We drove GX's that felt awesome, but they were $18k! I drove GX's that had all the service records from the dealer and yet still had blown suspension and other problems. I ended up paying ~$3.75k for my Montero and thus far it has all the dings, dents, and deferred maintenance you'd expect from a 15 year old rig, but it still feels tight, and operates well. I can buy an awful lot of maintenance, repairs, and goodies for the price difference. I never found a GX under about $14k that was in reasonable shape. I also found dealers have no idea what to do with Monteros, I offered ~50% of listed and got the truck.
Finally, if you work on your own rigs, I generally do, every single problem I've encountered (bad temp gauge, locked glove box, etc) has been solvable with ten minutes on google, generally with zero parts required. Sure there are tutorials on timing belt replacement for both the GX and the Montero on youtube, but when your random doohickey breaks, the GX forums often say "well take it to the dealer" and the Montero guys say "grab your tool box and expect to spend $30 and an afternoon.'
I can't speak too much yet to the long term reliability and performance, but coming from a 1985 Nissan 720 pickup, it really feels like Mitsubishi just channeled that old school utilitarian engineering approach and built something that works, is fixable, and generally gets the job done without much flair. And for me and my family, so far it's been perfect.
As soon as I get the Nissan sold off I'll be starting a build thread, but I'm going to try and do it a little different so it may take me a bit to get it all figured out...
