GPA Bb5 vs. Bc4

I'm playing the grand prix attack, and i can't chose between Bb5 and Bc4. I have played those two lines, and those are all  comfortable for me. So which is better for white?

It's too bad no one ever answered you. I'm trying to answer the same question.

It depends if black played d pawn or not.

1.e4 c5 2.Nc3 Nc6 3.f4 g6 4.Nf3 Bg7 and here, probably Bb5 is better than Bc4.

If Bc4, then black can go for e6, Nge7 and d5.

Whilst 1.e4 c5 2.Nc3 d6 3.f4 g6 4.Nf3 Bg7 5.Bc4, now its different. If Black goes for d5, he would have lost a tempo with d6...

Here is a rule : if Black is well placed for d5, prefer Bb5. If not, prefer Bc4. But there are exceptions...

I've just mentionned positions where black played with g6, and there are many other subtleties...