It all depends what the XJ is used for and the trade-offs you can accept.
The TT is invisible in 2WD, and also 'smooth' enough to drive around in 4-hi with the rear driveshaft removed (if need be...I did need to -+500miles) Off road in my MJ it was great 85% of the time. (mostly muddy rocks in hilly terrain) Quite better than open, but as others point out... NOT a locker. I also had a spool rear pushing us along. On the road in what little snow I encountered, it was uneventful... enough to shift back into 2-hi to 'have fun' when the roads were clear of traffic.
The front EZ Locker in my XJ was invisible in 2wd also, I DD it along with the same spooled rear for 15k? +- but for the 100 feet of dry paved road & dirt shoulders after I shifted-on-the-fly @ 30 MPH, I felt more at peril than I have in a long time... I can't answer why I shifted into 4-hi either
I chalk it up to a bad idea that leapt upon me, and she jumped out the window just before the near-impacts. I added that to my list of "never again is too soon" stuff. I couldn't imagine driving on public roads in locked 4WD other than in thick- blizzardy stuff. Off-road it worked really well... world of + difference. Much wider turning radius, but once on it's line, it was great.
I like the idea of selectables... but for my $$$ (invested already,) I'm reusing my TT front & gears for my 90% dry/5% slick DD, 5% 4WD off-road 242 XJ... Maybe have to take a strap or cable here & there, but who doesn't...