Both men have split time over the course of the season, with Ramon having the reputation of being the better offensive force, and Hanigan being the better signal caller behind the plate.
(In my opinion, though, Hernandez doesn't get enough credit for his defense, but that's a different topic).
Hernandez has performed just about as well thus far as anyone could have hoped. He has come up with numerous clutch hits, and at an age where many players start to slow down, "Razor Ramon" is putting up one of the finest seasons of his career at the age of 35 (.322 BA/10 HR/26 RBI).
His counterpart, Hanigan, hasn't handled the bat quite like he normally does, as his .250 average is a career low for him thus far, but he still has a .351 OBP. Grinding out at bats is a trademark of his game, as is putting in excellent work behind the dish.
Of the numerous problems of this team, catcher is one area in which they have been able to count on.