Honestly, I would avoid Glocks.. They're very popular pistols, most of that is because they're very good at marketing, and they're cheaper. If you're looking for that price range, I would suggest looking for a Springfield XD or a Smith and Wesson M&P.
What type of experience do you have, and what caliber are you looking for? Glock 27 is a .40 Cal, which is a pretty snappy round. It's a bigger bullet, and very fast moving, which means more recoil, and harder to get back on target for followup shots. Honestly a 9MM and some hollowpoints are good enough to stop anyone.. If you're feeling you want more then you could probably look towards a .45.. Easier to get back on target than a .40, and .40 is a round that people are starting to move away from.
That being said, it's a good round if you learn to master it. I carry a .40, and I love it. The gun I carry is a Sig Sauer p229, and I love it. It's a little bigger, but I'm able to carry it in the California heat and not print (although it can print if I'm not careful about what I'm wearing), and the weight balances the gun more. Some people don't like the weight, but I've never been bothered by any of that.
It's a little more expensive, but I'm a believer that it's better to wait an extra month or so and get the gun you want, rather than settle. The other thing I like about sigs is that it's double action, and as far as I know a striker fired pistol (Glocks, XD, M&P's, and others similar) cannot be DA... There aren't any that I'm aware of anyway. The problem with that is that most (such as Glocks) don't have a safety either, so you're more likely to ND when drawing from your holster. Obviously nobody wants to do that.
I like a safety as well, but others worry about fumbling with that in a time of crisis... I would counter that if you fumble with a safety, you don't have enough training, but to each their own. That's one of the things I like about a DA pistol though, there's a rougher trigger pull for that initial shot, but the follow ups are nice a short.
Glock triggers are junk, if you do get one, drop in a new one.. M&P's aren't great either, but the Apex trigger is much smoother. I don't mind the Springfield triggers... Don't skimp on a good trigger though, it's going to make you more accurate.