well for one there are no pre-97 mountaineers, and there are no pre-96 v8s-- just two things to keep in mind.
also, the body style change (rounded rear hatch different tail lights occured for both vehicles in 98)
other than the badging on the vehicles the mountaineers are very comparable to the explorers. it is possible to have a mountie with no sun roof, cloth seats, and a V6 with an open diff. while it is also possible to have a v8 powered, leather, moonroofed, explorer even in the xlt range.
the one big difference is in the grille and headlights. the mountie has slightly "better" headlight lenses and a different layout up there.
another small difference is that the mounties have a lot of ugly cladding on them if you get them in the wrong color. the better colors have the cladding but it looks nice.
also, look out for the early ones because they can have the 160 hp V6 rather than the newer 20X hp 6.
if i were you i would try to find a 98 explorer or mountaineer that had the options you like and a cheap price. personally i'd want 20.000 to 50,000 miles and a price tag of under 20,000 (asking price) and then work from there.