Martin hasn't hit above .250, nor hit more than 7 homers, in each of the past two seasons. He's hitting well this first week, but I doubt it stays that way. For what it's worth, here are some projections:
RM: .253/.358/.361 with 10 homers
JPA: .230/.273/.432 with 25 homers
RM: .270/80/.398 wiit 12 homers
JPA: .235/272/.462 with 21 homers
Both will kill your BAVG, whereas RM offers OK OBP. But JP's power is just so much more dominant...I feel you could find another Russell Martin on the WW at some point, but JP will eventually be picked up, and the chances of finding another catcher with 20+ homer potential will be basically non-existent.