As I've said in the past, they'll both get plenty of opportunities to get a similar amount of catches and yards. To me the battle for the no #3 WR is something that the press and fans value more than the coaches. Despite dropping more balls (by amount thrown to and total amount), Jones still had 100 more yards than Nelson (granted Nelson was hurt more).
I've heard from some that Nelson looks a little better than Jones in practice, but it's never the same speed as a game. Frankly, if Jones gets his catching under control I think he'll have more yards again. I expect both to be in the 350-550 yards range provided the rest of the targets are healthy.
But given Jones is going to be a free agent this off-season, I would say he's battling himself first for a new contract and then Nelson in a WR opportunity cost decision. But, they could resign both to more short-term contracts.