My beloved S&W really screwed the pooch with the sigma line. Upgrade to the M&P line. Also the .45 is a powerhouse compared to the quick little 9mm. For defense its a proven better choice.
The Sigma is an inexpensive pistol. I have two and I can shot them well. Not everyone can say that. They feel great in the hand but the trigger takes some getting used to, a lot of getting used to for many people. I have very large and unusually strong hands so the trigger is no big deal for me. My wife does not like either Sigma. Trigger just too much for her after 50 rounds or so.
I do not know the going price for the Taurus but it would depend a lot on which model. An early 9 F or C with night sights and very good-excellent condition? I would say go for it. A "V" model only cost about $235 new so probably not. The models with an "E" have the light rail and are worth a few cents more.
I have had mine for about 13 years. I bought it because it was inexpensive. It came with two 10 round clips. During that time I have used it to qualify for my CHL and to renew my CHL twice. It mostly stays in my vehicle for a just in case gun. Everbody is right about that trigger pull, but I have always shot perfect during qualifying and renewing.
Therefore it serves its purpose for me.
One of my guns is a 9mm sigma. I have had no problems with it. Shot it many times and have never had a problem. I am a Sig Sauer fan but purchased the sigma so my son could go with me to the range and shoot something and it was inexpensive. In the end, do what you think is best based on the information you have received from your question.
The Sigma is a Glock knockoff. So much so, that Glock sued S&W for copyright infringement of the trigger system....and won! S&W tried to copy the Glock success on the cheap, but failed. The choice you have given is between the fire and the frying pan. Taurus is problematic as well, and the customer service on warranty work is the worst.
Take the previous advice and get a Glock or an M&P. Both top notch pistols.
Carrying/owning a pistol is a serious thing, don't you want the best you can get?
I have the Sigma 9mm. I had to polish the sear, slide and most moving parts and modify the springs to make it work well. However, it is very dependable and shoot faily accurate.
I fired a buddy's Sigma 9mm last weekend. Back of the yard by the fenceline, we set a target at about 12 yards. First guy shot six inches low. "Ha, you yanked it." Next guy was the owner of the gun - again six inches low. I picked it up, placed the front sight on the target, and then lowered the rear sights to where I could just see the front edge of the slide and drilled the target.
At normal handgun range 6 inches ain't much, but I'd kinda want to hit what I was aiming at, ya know? I wonder if it was just that pistol or if it was an overall manufacturing defect.
That said, the pistol is very light, but the recoil isn't all that bad.
With my Sigma 40C I routinely pi$$ off my step son by shooting 12 ga hulls off a board at 25 yards. All the while he is trying to bring them down with his 10-22 (prone). Kids! if the trigger is not a part of an X-Box controller, they yank it every time.
I used to own a 40ve(sigma "enhanced" version). It shot ok for me but did have a terrible trigger. The lack of "real" safety kind of turns me off to this series as well as all of the Glock pistols. At least the P99 I own now has a decocker and a firing pin indicator. Personally, I would not trade any gun I own(even a 22) for that gun.