Half Height Low-profile AGP or PCI card?

[compcons]

I have a Dell with a half-height AGP slot and 2 open PCI slots. So, I need to make a decision. Which is less slow?

PCI bus with a BFG 6200OC or AGP bus with a 64-bit Asus 6200? I guess its a question of which bottle-neck is more restrictive; memory (128 vs 64) or bus (PCI vs. AGP)?

Thanks,
EH