Considering only concealed carry,Would you rather have 7 shots of 45 ACP(Model 457)or 12 shots of 9mm(Model 6906) ? Both pistols would bo loaded with hollowpoints.

I love making people mad with this topic!!!
It is not about caliber size it is about shot placement..most gun fights happen with in 3-7 yards and end with an average of 3 rounds..As a cop I have seen more people killed with the following rounds:
.22,.25,9mm
So with that said and people copying my statement as a quote and commenting on it..LOL I personally would have to choose the .45acp.. Because it tends to stay inside bodies and tumble causing more damage than just a simple entry and exit wound a 9mm may cause...Other wise I am carrying a .357mag for the penetration and the power....

Either, I practice and shoot between 250 to 500 rounds weekly so I'm very confident in my abilities and have been involved in stressful situations involving handguns before. Caliber means nothing, shot placement does, of course that doesn't mean because your good you can carry a two shot 22 derringer. 90% of the time I carry a 1911 as thats what I shoot best but recently I have started carrying a HK P7 in 9mm and am very impressed with the gun and it's abilities so it's been getting a lot more carry time.
Carry what you are comfortable with but train, train, train then train somemore!

Before I got my 4516-1 last month I would start to carry my 3913 now being that spring and summer is coming. I more then likly will switch off between the two. See how the 4516-1 covers with lighter clothing and no coat! For summer carry the M&P40 I use to carry most of the time would print bad on my small frame.

Which ever gun you're most proficient with and can afford to do the most training with. Money is an issue for a great many people, and 9mm is simply cheaper. (I'd obtain and carry a mid size 11 to 14 shot .40SW auto over either choice personally. The .40SW rather puts a crimp in the old 9 vs. 45 debate which is why it is no longer staple filler material in gun mags. One of the double stack TSW .40s can be had that holds 11+1 and is about the same size as a 6900 series 9mm.)

To a certain extent, it will also depend on what school of training, if any, you pick. If you learn "shooting the tee" or a variant there of, it lends itself better to hi cap autos. Any of the "stitch the bad guy" training programs work better with more rounds on hand.

I'm confident with either, but I'm more comfortable with a .45. Capacity doesn't matter, I know how to reload if needed.

Shot placement is non-existent, unless you are attacked by a stationary, oversized piece of paper on a well lit range. Actual assailants are either covered in fat or are skinny crack addicts. They bob, weave, duck, woddle, stand oblique and do what ever possible to not get shot. Actual victims are off balance, half-asleep or scared shitless. The odds of the victim hitting the assailant are high, but the odds of hitting a vital area are low.

I believe in using the biggest bullets to inflict as much damage as possible, hoping it is enough to break off the attack.

With modern ammo there appears to be little statistical difference between 9mm and 45ACP. Both are equally good/bad. Like many have commented here, shot placement is king. I chose 9mm because my 3913 is what works for me.

Most folks shoot the 9mm better. As others have noted, with quality ammo, terminal results are pretty much the same. Edge to the 9. BTW, do some practice with one hand only (both shooting and support hand), your other may be otherwise occupied when you need it.

However, there's other factors. Do you live in an area where LE response is slow? Gang activity? With mulitple assailants a growing problem and response time longer than you may wish, the amount of ammo on hand may tip the balance. Do carry at least one spare magazine, 2 if they're 7 rounds.

No one has ever complained that they had too much ammunition.

Shorty