lunch box locker refers to any locker that replaces the spider gears, IE: aussie, lock-right, ez-locker etc. Full locker replaces not only the spider gears but the carrier as well. IE: ARB, OX, Detroit. Not sure what would happen with a lunchbox in the front of the JK. ON my TJ, I only noticed it when there was a very sharp low speed turn.
I can tell you having a full time locker in the front on snow covered roads sucks. Want to pull you left or right. I have also had a full case locker in the back only and it was fine in snow, it did however "bang" on slow speed turns. Sort of like a mini cannon going off. If you can I would save up for a selectable locker such as the ARB or ox, as its very nice to have control over the lockers. Of all the one's I have run I enjoy the ARB's the best. But for cost the lock-right was fine.