The battle for catcher is turning out to be a pretty good one. I've read that the Astros are committed to Humberto Quintero as the backup, but why?

Why can't the Astros have, provided they produce this spring, both J.R. Towles and Jason Castro on the opening day roster and split time right down the middle between the two. I'm not a big fan of Quintero and I don't like that by some accounts he's already been given an opening day spot. I believe Towles/Castro can be just as good defensively or slightly below what Quintero provides, with the potential to produce much more at the plate. I like the idea of a Towles/Castro platoon better than one with a Towles/Quintero or Castro/Quintero split. 

Stats through spring training:

J.R. Towles : 5 Games 15 AB 4 Runs 8 Hits 5 XBH .588 OBP .867 SLG .533 AVG

Jason Castro: 4 Games 12 AB 0 Runs 6 hits 1 XBH .462 OBP .583 SLG .500 AVG

Humberto Quintero: 3 Games 9 AB 1 Run 1 Hit 0 XBH .111 OBP .111 SLG .111 AVG

*none have taken a walk

This could take some of the pressure of both Towles and Castro and create some competition between the two through out the season, while still developing as a catcher.