Make sure that this head to head battle is fair:
Same type/style/modded truck (read same lift, tires, suspension, etc)
Then have one locked and one unlocked.
Anything else is simply posturing...
Then try straight mud runs, sidehills, flexy tank traps, rocks, snow, etc...
Unlocked will do better in some situations, locked will do better in others. A wise driver will try it all, learn what works in what situations, and what does not. Then will select the "most" correct setting (gear, locked/unlocked) for the situation ahead. This of course does not ensure ones getting through. Of course, not near having tried it all...I have tonnes to learn.
Wayne, if you are saying if one knows how to drive an unlocked truck it can go many places (and many people think this is the best way to learn to drive...then get lockers) locked trucks go...you are correct, but not always!
NickW, if you are saying all things being equal (vehicle, terrain, driver) a locked vehicle will go deeper...then you are correct most of the time, but not always! (slippery sidehills being one where unlocked may be better).
Of course if it is simply a friendly challenge to get the trucks out, have fun, get stuck, hoot holler and learn...then have at r...
gb