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.