Overall CERA:
Wong 4.03
McGuire 5.94
The reason McGuire's is so much higher, even though he does better with some pitchers, is obviously that the ones he does badly with are all starters, which translates to a higher volume of innings.
Also, the reason McGuire has not caught Houck, Whitlock or Paxton is that either they asked for Wong, or management made the call. It doesn't reflect well on McGuire, in any case.