Think back a little. How many OFFENSIVE all-star catchers have stayed behind the plate? Pudge Rodriguez, Bengie Molina, McCann, Mike Piazza, ... Most teams look for a way to get the catcher with a superb bat out from behind the plate. So, I don't see the idea of moving Santana permanently to 1B or DH as an insult to his defensive skills. Most fans have no idea how hard it is to be a good defensive catcher. It takes many years to develop the basic skills (blocking pitches in the dirt, mechanics for throwing out base stealers, calling a good game, blocking the plate effectively when runner trying to score).
You shouldn't expect any young catcher to be "GOOD" defensively, it develops over time. Guys like Tony Pena, Benito Santiago & Pudge Rodriguez are rare! Guys that come into the league knowing how to play the position well and are solid at the plate come along once every ten or twenty years.
The argument for Posey being the better young catcher because of his defensive skills is weak because EVEN THE Giants consider moving him to 1B to avoid another injury (maybe career ending type).
Honestly, a GREAT catcher should not even be able to battle for a batting title, HR title, RBI title or whatever. A GREAT catcher is a catcher that wins games through his defensive skills and game-calling/rapport with his pitchers. A GREAT catcher is like a coach on the field. He talks to his teammates, coordinates strategy on the field, controls the tempo of the game, etc.
AND TO THE POINT:
As long as they are both playing catcher about 80+% of the time I'd say Posey is the better CATCHER. But which is the better overall PLAYER playing catcher? I'd say that Carlos Santana is the better player playing catcher because he is not known to hurt his team when he is catching ANDhis offensive production puts his pitchers at ease by pitching with a lead or knowing they are always in the game if they give up 4 or 5 runs or less. Unless you've ever been a pitcher you don't know what this means. PITCHERS LOVE RUNPRODUCERS IN THEIR LINEUP!!! THEY'LL BUY DINNER FOR THE GUY THAT HITSA 3-RUNBOMB FOR HIM AFTER HE JUSTGAVE UP A BOMB THE INNING BEFORE!!
CARLOS SANTANA is one of the best hitters in the game ALREADY even after a torn ACL, surgery and rehab! And he's only 25 years old!! There have been HOFs that started their careers at 25! Carlos Santana is one of the best hitters in the game, he's young and he happens to play catcher. Therefore, CARLOS SANTANA IS THE BEST YOUNG CATCHER IN THE GAME.
Weiters and Posey are very close though. They can catch up this year. Unless SANTANA improves like most people expect him to. Then there will be no close to him