The Sigma is pretty much reviled in the annals of hadgun lore. There is a reason your buddy is selling it, my friend. At $200, it's about $199 over-priced (IMHO). The trigger is horrific and the gun is a little tough to maintain. I'd pass on that one.
The Taurus--I'm tainted. My very first centerfire handgun was a Taurus PT945. It was hideous for accuracy, and when parts started flying off of it during range time, I sent it back, got it fixed, and sold it without firing another round from it. Since then, any Taurus auto is poison for me. Revolvers? Okay. Semi-autos, no way in heck.
For $400 you can pick up a police turn in GLOCK and some ammo, and be far better served than by either of those guns.