I love my 45acp SigSauer P220. I also love my S&W Model 13 357 magnum. Choose whichever of the two you like. 44amp is so dead on target with his post. If you know how to shoot, and hit your target, then over-penetration is practically a non-issue. If you can't hit your target, then it doesn't matter if it's a 22lr, 38spl or a 44magnum; you are just as likely to hit an innocent bystander.
Contrary to what some people will want to say, you are not going to be in the same situations and scenarios that police are in. Your whole purpose of carrying a gun is for self defense, with a small portion possibly to protect a loved one or another person. These situations don't have you shooting at someone in a crowd of people. You're not the police making a drug bust, handling an impromptu hostage situation, etc... If you need to draw a weapon, and you point it at someone, you should do so with every intention of pulling the trigger. You don't have a gun to try and scare the bad guy away. if you pull your weapon, and point it at someone, it's because you are GOING TO PULL THE TRIGGER. If the situation dictates that it may be more risky to pull the weapon, then don't. You don't want to expose your cards to the bad guy by pulling out a gun and trying to bluff/scare him into dropping his weapon. So, being you're going to pull the trigger when you draw your weapon and point it, you're already in a position where you're confident of hitting your target. And you're in a situation where you don't have a bunch of innocent people standing immediately behind him. So any over-penetration, if any, will be minimal. And even if it's there, the chances of hitting someone and injuring them is even less remote.
Pick the gun that you like, want, and most proficient at. Any talk of "over-penetration" is over dramatic. If you do your part, and only pull the weapon out and point it at a person when you are definitely going to pull the trigger, and you're confident in your proficiency, then over-penetration isn't an issue. If you're not proficient, or you think that you might not have what it takes to maintain your composure when pulling out a gun, then you need more practice. Physically and mentally.
And for the 357 magnum, I definitely load it with 158 grain hollow points. It's the perfect round. The 357 magnum is the perfect cartridge. Yes, I could go all the way up to 200 grains, or all the way down to 115 grain, but 158 is in my opinion the best. That is the size bullet that the majority of revolvers were designed around. I don't need 1500 fps with a 125 grain, when a 158 grain heavier bullet is just as, or better, at 1300 fps. That's what my 357 magnum 4" revolver was designed around. That's what I use. Just like my 45acp was designed and based around the 230 grain. I don't need a 165 or 185 grain bullet. Now, if you're a small person and can't handle the 158 grain 357 or 230 grain 45acp, then by all means look at the 38sp+p or a 165 grain for the 45acp. But if the size of the bullet isn't an issue for you're accuracy and handling, then use the 158 357mag or 230 45acp.