First of all do an archive search of the dozens of times this has been brought up in the past. As the proud owner of a 1997 TJ with 105,000 miles on the 2.5 L 4 cyl, I can say this: Get whatever you can afford. The 2.5 will be weak if you put some 31+" tires on it, it will struggle at highway speeds, it will get the same gas mileage as the 6, maybe even a bit worse.
Take that engine off road, and in most things (deep mud requires HORSEPOWER) it will perform as admirably as can be.
Good luck to ya man, but trust me, ya want that 6!
Daniel J Fenti
Owner - NC Transmission
2004 WJ Overland lightly modified
Boat Drinks OffRoad Co-Founder