A few things I hate seeing in caliber war threads...
1) Shot placement is key. With very few exceptions, shot placement is going to be similar between 9, .357 sig, .40 S&W, and .45 ACP. The only time it won't is if you can't handle the recoil (a valid possibility, especially for smaller shooters).
2) It's the gun you have with you that matters. This argument makes sense if you're getting mugged, that the 9mm on you is better than the shotgun at home. However, when you're selecting carry hardware, "the gun you have with you" is the gun you planned ahead to bring.
3) People who disagree with me (okay, kidding on #3).
Personally, I've approached caliber wars in a few different ways. First I asked "what's best?" Then I said "I think this is best." Now I'm looking at things and wondering if a 10-round limit would affect my consideration, and it probably would be. I'd be more likely to carry a small 6-7 round pistol if limited to 10 (instead of comparing it to a 15+ round pistol), in a compact carry pistol I'd be more likely to opt for .357 sig or .40 S&W, and in a duty pistol I'd be more likely to pursue .45 ACP.
As it is right now, I prefer 9mm. The ratio of expanded-to-original diameter is bigger with 9mm than .45 (compare 0.65 to 0.36 vs. 0.77 to 0.45, which is the average of what I've seen from gel tests or 80% increase vs. 71%), and the difference in size isn't all that great. Capacity is the biggest factor for me, but cost and recoil play a big part as well.
Zardaia, I wouldn't be so sure. Look at the woman recently who shot an attacker 5 times in the face with .38 spc, the rounds penetrated down through the man's torso. (She was hiding in the attic with her kids, explaining the downward trajectory. Hit with 5 of the 6 rounds in her revolver). The fight stopped, but only because the attacker gave up. According to reports he was begging her to stop shooting and left the scene of his own accord, only to be found by authorities after crashing his car. Granted, .38 is a bit weaker than even 9mm, but you would still think 5 shots to the face would put someone down right there.