are 9mm, .40 and .45 really all the same?

Since there's a push on for small carry pistols and everybody seems to want to buy them for carrying (not much for shooting, but a lot for carrying), there appears to be a feeling running through the Intardweb that the 9mm, .40 and .45 are all the same, with all kinds of gun store BS sayings to go along with defending the little guns.

Consider this: if all you could have, if the only option available was eight rounds, would you want them to be 9mm or .45? Not all the same.