I wouldn't put a locker on a stock Cherokee. You'll get much farther than ground clearance will allow. (i.e. stuck)
On a lifted Cherokee, I would do both (but I have only done the rear).
I've run two years without lockers (the first year on 235/75R-15 and a 2" budget lift, the second year with 3" lift and 31"s) and one year with a welded rear.
Trust me you don't want a welded rear on the street. Even in a "long" WB Cherokee. Traction is amazing though. Until your tires wear out.
I would put a locker in the rear first. On steep hills, the weight will be on the rear and that's where you want the traction. On steep downhills you don't need the traction (as much). On "flat" stuff either will add traction. So you have one that matters and two that don't, so go with the one that does.
The downside of no front locker is that ledges are harder to climb. The downside of a rear locker is the rear gets loose sometimes when you don't want it to. you really need a locker in both end. If you can only afford one at a time, I would do the rear first. If you can afford an Ox or ARB, etc, definitely do that.
I've got to decide what to do next, but I think the welded diff is coming out... it's just way too hard on the tires and street manners are pretty bad. My wife almost refuses to drive it... she loved it before. I put less than 10k miles on it a year... probably 7-8k and... in 16 months I have gone from ~70% tread to 0% (and I mean total slicks).
Before I do anything else I have to decide if I'm putting on larger tires ($$$$). If not, then the rear diff is getting replaced by an Ox, ARB, or some other selectable locker - those might be the only two available for the C8.25, and the front will probably get a Lock-Right or Aussie.
If you have a D35 rear... don't put a locker in it. It's junk. Get a 29-spline C8.25" (at least) or go with an Exploder axle (F8.8"). The 8.8" is a big pig and will take 35" tires on a light Cherokee. The 29-spline C8.25 is no slouch... it goes under Durangos and Ram 1500's. It's good for 33"s.
As for the front... if you have a 2000-up... forget locking the front low-pinion D30 axle. Swap it out for a 1999-down high-pinion D30 from the mid-90's to 1999 (don't want the central axle disconnect and you want the big u-joints). It is as strong as the low-pinion D44 from the TJ Rubicon (same axle size and u-joints).
I have a chr 8.25" in the rear end as mentioned...I would love an ox but that is really expensive and only would do that with regear and axle shaft upgrade.
I was thinking of running 235/75/15 with aussie...why not bother with lockers on a stock jeep? doesn't make sense to me...
