I'm going to go out on a limb here and say, Bogut.
I can think of like 10 centers off the top of my head I'd take over Bargs probably another 6 or 7 if I actually thought it out.
Edit: Bogut is one of them
I guess I'll be the first to say Bargnani. Bogut can't stay healthy. And 12 points a game? We'd be dead last offensively and could probably set a record. Sure we get good blocks and rebounds, but I'd rather get a more stable center who can put up slightly lower numbers and play many more games while playing with Bargnani. Bargnani wouldn't seem so bad if we used him properly, he is who he is.
Defence only gives you a chance to win. Offence wins games. You can hold a team to 60 points, but if you score 40 it doesn't mean anything.
Offense only gives you a chance to win. Defence wins games. You can score 100 points, but if the other team scores 120 it doesn't mean anything..
This could quite easily become a chicken and egg discussion.
Personally, both are important. To win you need both.
If you are going to rely on either one, you better make sure you are the absolute best at which ever you go with.