There's a real simple solution to the 9mm vs .45 debate. Get a .45 and keep a 9mm as a backup.
Actually, I carry a 9mm and keep my 45 as backup.. I prefer carrying a 9mm handgun with a 17rd mag plus an extra 17rd mag of 9mm +P HST HP, which if you study ballistic tests, you will see the penetration and energy ratings are very close. With modern bullet technology, rounds like Federal HST will expand to a similar to diameter as a .45 round and create a similar size wound cavity. They have done studies in gel, as well as in animals the effectiveness of HP 45 and 9mm rounds and the two are so similar that it doesn't seem to me it can justify the extra expense and weight of carrying a .45. Now, if we are talking FMJ rounds, the 45 obviously is a better choice than the 9mm, such as carrying Ball ammo used many years by the military.
Also, considering how much more expensive it is train with .45, I prefer carrying the 9mm as it is cheaper to shoot and I can train and be more proficient with this round. You will most likely do more shooting and practicing with a 9mm than a 45 round.
I guess, my only comment is that if I was traveling through Kommiefornia, where hi-cap mags are illegal, maybe I would consider carrying my 45, with 10rd mags with me instead.
Sorry, to hijack this thread.. 9mm vs 45 probably can be a nice long thread in itself.