I think that is a hard question to answer.
It seems to me, in general, that defense is not too important in PB.
I have seen catchers with terrible arm ratings gun down my baserunners, while my catchers with better arm ratings can't throw out Mirabelli!
I have had Helton at 1B for 4 teams, with 3 errors all season in real MLB play...and in all 4 teams have 10+ errors.
I have seen teams play Delgado at 3B all season...and his defensive numbers were more than adequate.
So, my impression is that PB does not recreate defense too well...so go for the hitting!