i saw you already bought, but since I vote for the 9 I will jump in and help you avoid remorse!
Listening to MB a while ago I found that I agreed with his lots of hole theory and 9s are easy for most to shoot. I wanted something that other family members could shoot as well. hard to argue with ammo prices and the more I have read on ballistics it comes down to about 95% shot placement and 5% caliber. So i stated with a 9.
I love 45 and since I can only have 10 rounds max here in the CA paradise I have a 1911 as my primary match gun and started my son on the SR9. I don't think I would want to carry a 1911 all day every day if I had the option so a lighter 9 makes the most sense to me.
Interesting thing to me is peoples feelings about the .40, I know a lot of folks shoot it at matches for capacity reasons at major PF and I can understand the LEOs going to to it for the service pistols as a "better stopper" out of a heavy gun means the recoil is manageable for most. I just never hear too many folks that are attached to it as the other two rounds. I wonder why?
Enjoy your choice.