Many different things you can base your decision off of. 96 is OBD2 and the 91 is OBD1. Depending on your area, the 91 may not require emission testing as opposed to the 96, which most likely does require it.
If maintenance records are good between the 2, mileage is just a number. These motors are very strong and if taken care of, can see in excess of 300K.
Check both for rust! The floors and rocker panels are very common. Although youre from down south, it can still present itself as an issue because of the lower layer below the carpet holding water and rotting out the floors.
And finally, have them both inspected by a mechanic. On vehicles this old, its always good practice to have them checked out so you don't miss anything. If its a good/reliable car, the seller should have no problem with getting it checked out. If it is a problem with them, that's usually a good sign not to purchase the vehicle.
1996 Jeep Cherokee- Project-- Rusty's 8in long arm, SYE kit, Teraflex driveshaft, Cragar soft 8's 15x10 with 33x12.5 Firestone Destination MT's, Eaton Tru Trac in the front