The .45 certainly isn't a skimpy round, but it's limited in a number of ways. Some people like the 230 gr ball ammo, but I'm convinced the 185 JHP is the way to go. I loved going out in the middle of nowhere and shooting at clay pigeons 100 yards out with my .357 Security-Six. Even with a 2.75-inch barrel, I could make life extremely uncomfortable to a mansize target at that range. One woman who had never shot before was kicking up dirt all around the clay target and would shatter it quite often. The .45 has the trajectory of a bowling ball. The 9mm runs much flatter and penetrates well. Many guns also let you shoot many more rounds than the .45.
On forums like this, we tend to sometimes become preoccupied with the downside of a particular gun or round. But reading as many news reports as I have about people successfully defending themselves with guns, I have yet to read one where either the 9mm or .45 was inadequate. Indeed, it's amazing the number of people who have successfully used the lowly .25 ACP or .22LR to drive away or kill their assailants.
In most cases, people don't actually have to fire their guns at all. One former burglar who went into the home security market told his story of his last break in. He said he was stuffing items into a black plastic bag in a home he thought was empty when he said he heard the scariest sound he had ever heard during a break-in -- that of a slide being released. He didn't know what type of gun it was or the caliber, but he knew what it was the instant he heard it. He was so frightened that he left the bag and fled. "If I had wanted to meet people," he joked, "I would have been a mugger." The point is, he wanted no part of being on the wrong end of any firearm.
This isn't to say that caliber is unimportant, but a 9mm hollowpoint isn't anything to be taken lightly. I will say that based on what I've read and heard, the .40 hasn't lived up to expectations. It was supposed to outclass both the .45 and 9mm, but in the end just didn't quite make it. Not that it didn't get a following...it's just that it failed to reach that "perfect storm" kind of a thing that the .357 125gr JHP did. One federal agent complained to me that a single shot to the chest failed to stop a 40-year old woman who was threatening agents down South somewhere. And there were other incidents where it didn't work out too well.
The 9mm has seen some vast improvements over the last few years and is a popular round. My 659 S&W is a great gun, especially with a 20-round clip. Who needs sights with that many rounds? Just close your eyes and keep shooting!