Excaliber wrote:I'll take a stab at trying to provide some useful information on a very complex topic without writing a book with the caveat that the information won't be complete and others here will help fill in the gaps.
No handgun round can be counted upon to stop someone with one shot. It just doesn't carry that much energy. That being said, bigger is better when caliber is concerned because larger rounds are more likely to produce incapacitation of someone doing something so terrible that he must be stopped right now more quickly than smaller ones.
Law enforcement officers don't carry 9mm, .40, and .45ACP guns because the weight is good for their exercise regimen. Those calibers have been proven over many years to be acceptable fight stoppers when the shooter does his part with good shot placement. You may have noticed that you've never seen a uniformed LEO with a .380 in his holster. The reason for that is he knows he can't trust his life to a projectile that small and underpowered. You shouldn't either.
Although our members will provide you with a long list of many suitable guns they're happy with, here's my suggestion for the newbie cheat sheet version of first gun shopping: If you're looking for a semiauto, any Glock, Smith & Wesson M&P or Springfield XD / XDM in 9mm, .40, or .45 that fits your hand and your concealment needs is a good choice. These and the more expensive Sigs are the ones most often seen in law enforcement holsters, and are all rugged and proven reliable. You can't pick a bad gun out of the many models on that list, and you'll have plenty to choose from without a lot of confusion.
Doc540's advice on "shoot before you buy" (e.g., rent or try a friend's gun) is a true bit of wisdom. Skipping this step leads to much expensive regret.
Your price target of $350 is going to be a challenge, but you should be able to come close to it in the used gun market with the 3 brands above. Their guns are rugged and frequently available used but in good shape. There's a lot to be said for going this route if you're on a tight budget, because you'll need to spend around another $100 or so on a good gun belt and holster, and more on ammunition to become proficient with your new gear.
What Excaliber said.
But I will also add the Ruger SR9(c) and SR40 to the list. Ruger doesn't have the reputation that Glock, S&W, and Springfield have in semiauto's. But this series from Ruger has gotten a ton of favorable reviews and I got my SR9c new for $380 which is close to your target price range.
</hijack>