IMO, I have said it once and ill say it again, I think someone just getting into wheeling should learn how "drive" offroad before they even think about lockers. You will learn so much more about what your rig capable of. (and the lather)
I didn't have a locked diff for the last 6 years. I wheeled, 3.5 inches of lift and 31s. It got to be where i could chase TJs around locked on 35s with my little XJ. Everyone thought I had lockers buts nope.. not in that rig.
This applies to rocks and trail running to me anyway. Mud-who cares, not much skill involved there.