Kendall's consistently been a .300+ hitter, so I'd expect him to heat up soon enough. Also, Oakland can't stay quite this bad for the whole season, so presumably the rest of the lineup will heat up as well and give him plenty of runs.
Inge, on the other hand, is bound to cool off a bit. The fact that he plays every day will naturally give him a bit of an advantage in R, HR, and RBI, but Kendall probably gets more at-bats than any other catcher, so that's not as big a difference as it would be with other catchers.
I do think Kendall is the better hitter, but I'll also admit that Detroit's lineup is a lot better than Oakland's, so that could mean he'll get fewer runs and RBIs. Inge also has more power, so if that's a concern for your team, that could be another reason to go with him. It's awfully close, to be honest, so while I'd expect Kendall to have a higher BA, I wouldn't be surprised to see Inge winning the other categories.