1911greg, you will soon notice that when it comes to effectiveness, no one can agree on a thing. Some people say light bullets and high velocities are best, other heavy large bullets. Some people swear fragmentation is key and other talk about weight retention. There is one thing that no one argues, rifles are much more powerful. Consider the 223 Rem round, it's a very weak rifle cartridge but it has almost 1300 foot pounds of energy, while 45 ACP has 350 to 500. Even a very powerful handgun cartridge like the 44 Magnum typically only has 700 to 900 foot pounds. By comparison, powerful rifle cartridges used to dangerous game can have over 5000 foot pounds of energy! It's not only about energy though, penetration must be appropriate for the size target and bullet design to be appropriate to expand of fragment.
When it comes to handguns, all the calibers except 10 mm, 44 mag and their more powerful cousins are marginal stoppers. The problem is that the recoil of these rounds makes them tactically useless because second shots are slow. The difference between 9mm and 45 cal is small, your best bet is to choose a caliber that you can shoot well because placement is very important. One short coming of necked cartridges is their tendency towards muzzle flash which can affect night vision and thus follow up shots. With that said, 357 sig is very fun to shoot and when I get some bucks I will be converting my Sig 229 from 40 cal to 357 Sig with a factory barrel.