I have run both the EZ and a True Trac in D30s. Both are Tractech products...good stuff IMHO.
The EZ-locker is the ez-ist way to go, and you dont have to mess with resetting the gears. Off road it's WAY better than the LS or open. Like said above, it'll 'plow' a bit in slick turns. I daily drove my 89 with spool rear & EZ front for a while...in 2wd I never noticed it other than some vibes from my driveshaft. The 30 EZ is #812A012.
The True Trac LS is IMO the best (only) choice for NP242 Jeeps that "need" smooth Fulltime 4x4 function . It worked great off-road 95% of the places (rocks & mud) we went, but I found it's limitations in a few (very rough) spots. It does require setting up the gears, and at $350? is approx $100 more than an EZ or other lunchbox locker. The 30 has 2 flavors, #912A374 (3.54-down) and #912A314 (3.73-up)
I plan to swap my TT into my 242 Limited when I regear it.