Hmm, I've thought about this several times. But given the lack of info on this game's leveling, it's going to be difficult to say.
I'd imagine that having better armor that reduces damage taken, better weapons increasing the damage given, special abilities such as: Anti-headshot, Invisibility, Speed Boost, etc; and possibly higher health because of your lvl would make it much easier to win a PvP over a lower lvl opponent.
To give those who are interested a better idea on the scope of this subject, why dont you check out the
RPG mod for UT2K4. You'll notice how much easier it is to kill once you've lvl'd up.