Sureshot129
Expert
A PF9 and a Sigma aren't really even comparable. They may be similar in price (the PF9 is actually quite a bit less normally) but they are not designed for the same use.
You need to figure out what you want to do with the gun before you narrow it down.
1000% this, if your going to seek training and have to shoot hundreds of rounds in a class the Kel tec will kick the crap out of you a single stack 7 round mag really isn't practical. I'm in the save a little longer and get a better quality firearm group.(Glock,M&P, or ETC) If your dead set on one of these two then the sigma is the better of the two but there are a lot better choices to be had if you save just a little bit more $$.