Their minutes are almost identical, and Hill's numbers are considerably better. But Hill also has a of a lot of upside - he will improve steadily over the next couple of seasons.
The first thing is that he will learn how to finish better at the rim. He gets there very well, and he puts up a lot of good shots that just don't quite go. He'll get better at getting those to fall, and that alone will put him up around 10 ppg, with the same bench minutes.
I haven't watched Batum enough to comment about his defensive consistency, but Hill doesn't take a second off on the defensive end. He's already a good defender, and he's getting better. He's smart, and he works his ass off.
Batum is doing well for a rookie. But a solid backup PG is a very nice thing for any team to have. The fact that Pop has given JV's minutes to Hill as a rookie says a lot. We're damned lucky to have him. Not lucky... it was a good pick by the Spurs' FO.