Results are just what I expected -- .45ACP and 9mm Para out in front, .40S&W a distant third. Kind of reflects real life.
I voted 9mm, though I have a great deal of respect for the .45. Why? Because you cannot yet squeeze a .45 ACP into a Kahr MK frame. Smaller and thus more easily concealed guns can be built around the 9mm. You can get almost any size pistol you like in 9mm. If you do want to carry a full size pistol, you can have more ammo on tap (my Ruger P95 carry gun holds 16). Why is that important, given that most authorities say only 3 shots are fired in the average gunfight? Well, you might not have an average gunfight. Faced with three aggressive crackheads, I want 5 rounds for each, plus a spare to be ready in the chamber while I swap mags.
Another plus to the nine is that ammo is cheap and plentiful. It's one of the most used cartridges in the world, and military/police standard in many countries. I can get practice hardball for as little as $6/box of 50 (UMC yellow box at Outdoor World in Orlando recently), while boxes of .40S&W or .357 SIG cost $14 - 18.
Without reopening the eternal stopping power debate, I will note that 9mms have been effective in thousands of encounters. Given a decently trained shooter, the 9mm leaves no reason to worry about being undergunned.
My favorite 9mm defensive load? Speer Gold Dot 124 grain +P.