I have to say that I go with MB on the .40- I honestly don't see the advantage in it. 9mm has some good defense loads. When you go up to .40 it's got more punch, but where I've been looking it costs the same as .45 acp. Admittedly, 45 acp is my favorite round, but I subscribe to the previously stated theory that if you're going above 9mm in semi auto your best move is all the way...45 acp. (with apologies to Desert Eagle fans)