I would go with the rear locker first (Unless your JKU already has the rear limited slip, then I would lunch box the front first.) If you are not going to re-gear or anything at this time, a lunchbox is fine. You won't want to waste the $$ on a full carrier locker to only need another if you cross the carrier break in a re-gear later. I favor a mechanical out back (I don't want it shut off). I prefer a selectable in the front to aid in steering as most of the time you won't need the front fully locked.
In my Experience with CJ front dana 30s.
"The CJ, ( auto mechanical front locker) while it did climb things quite well there was an issue with locking hubs almost every time out. It would break one each trip." -- FACT -- 5 bolt hubs are junk. I ran through my stash of spares in a years time, never again.
"Once the bullet proof hubs were installed" --MISTAKE!!-- Why? because this happens afterward: "the next issue was shearing the bolts at the locking hub wheel hub joint." THEN THIS HAPPENS: "The CJ also broke a axle u-joint, in some moderately challenging sections." And we can't forget this: Every time I ran a limited slip this happed: " when the rear locker failed to operate." Insert Maranda Lamberts "Something bads about to happen song" My tub still wears the scar from the last time I needed the limited slip.
WARN Premium Hubs are too strong, I prefer to run the Factory style Warn 6 bolt hubs, the idea is to have the lock out hub break before the expensive stuff and harder to fix on the trail items, IE: Axles, U-joints, Ball Joints... This is why I went from the WARN 6 Bolt Premiums to the 5 bolts, only the 5 bolts are way too weak and constantly fail, as experienced above and by myself. So my lesson learned is the medium grade OEM 6 bolts are the best option. Strong but not over strong. Also I use grade 5 bolts, when they break in the hub, it's not as hard to remove as a grade 8. Also I always carry a spare hub, lock out hub and bolts.