The Sigma is proof that even a gun maker like S&W can produce a stinker. I'd never trust my life to one. They have a terrible reputation. If you want a good, comfortable, relatively inexpensive 9MM I'd say ditch the Sigma and go with a Ruger SR9C. They can be had for about $399 new and $300-$325 used. If you've got $500 to spend then I'd go with Rocketgeezer's advice and look into a Glock, Springfield, and S&W M&P.
(Insert random tough-guy quote here)
"See my gun?? Aren't you impressed?" - Anonymous sheepdog
The hardware is the same, but the software is vastly different.