Depends on where your going to carry it and what size lift your running.
My 48" works ok on my XJ, the wifes XJ, but won't even come close to working on my MJ. It's to short. I have to run the tire-adaptor for it to work on the MJ. That works, unless I have a flat or something; as it's hard to take the tire off that your lifting on....
Well it's not like I have a roof rack or anything to mount it on... and I don't have a lift, but if I do get a large lift down the road I don't want to have to buy another... though they're probably not that hard to sell.
As mentioned above - the biggest deciding factor will be if you do lift down the road, and how much. I can still use my 48" hi-lift on my XJ with 4.5" lift and 33" tires, but it comes very close to limiting out. As for now I store mine in the cargo area side to side, since its a 48" it fits. Course this doesn't really answer your question, but if you don't plan on lifting too much I think a 48 will work out for ya.
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07 Powerwagon, pretty much stock besides Line X bedliner and dual exhaust. Quad cab, fully loaded (minus nav), etc
92 XJ sport, 33" boggers, 4.56 gears, rear locker, more to add
07 Arctic Cat 400 4x4, lockers front and rear, 2500lb MM winch