Had it all three ways
Open sucks, period, Folks who claim otherwise probably don't real-wheel much. I'd rather wheel a 5spd 2WD with a spool than an open/open 4x4 Jeep, but that's just me
True Trac Limited Slip = not bad. I found it's limitations on a couple trails, but for 90% of the routine east-coast trails, it did fine (backed up by a spooled 44 out back) It is going in the front of my DD with 4.10:1, but am undecided about locker or TT L/S out back yet. This XJ has a 242 AWD case and will rarely see any serious off-road... more of my all-weather car, so not much need for locker$.
Lunchbox Locker = invisible on road in 2 Hi, makes a world of difference off road on those 'other 10%' trails. Opens up a whole new world of real-wheeling potential, the only tradeoffs I found is a plowing while turning in the mud (on the gas) Not a big deal, just took getting used to and rethinking some 'old' lines.
Best of both worlds would probably be a selectable, but other than riding with a couple folks with them (Ox and ARB) I can't rate + or -. They seemed to work well is all I saw.
Since your 30 is to be a stepping stone, but you wanna run with the big dawgs... pop the $200 for an Aussie and have fun. Then as mentioned above, sell it to the next guy in line who wants real 4WD.