So I'm on my 3rd Disco 1...there's a ton of info out there and for the best stuff on that vehicle I would be remiss if I didn't mention Discoweb. Discoweb, using the search function (a lot) before posting.
That being said the basic separation between vehicles (94-94, CUX, OBD-1, 3.9L with a Dizzy vs 96-99, GEMS, OBD-2, 4.0L w/coils) is the starting point which gets to a series of questions:
-What do you want it for?
-How much do you want to modify it, for what climate, and for what kind of wheeling?
In general there is a school of thought that says the 94-95's are good b/c they are simpler (less electronics). The counterargument is that the GEMS can actually be dependable around the core of the electronics related to the engine (the other stuff...well these are Rovers).
My suggestion: do a lot of searching on a lot of forums/sites for the best low mileage truck you can find that has a quantifiable maintenance record.
My opinion: get a 98-99 D1 with the lowest miles you can find. The 94-95's are nice for some reasons but the 98-99 (a lot of folks will try to tell you there were no 99's) were the end of the build. Of course I live with the contradiction that I've had a 94, a 98, and now have a 96-but the 96 had 75k miles on it when I got it and it was meticulously maintained so I'm pretty happy with her.
r-
Ray