My knee jerk reaction is go for the Sig. It's just a better gun. Not to say the Glock is bad though. However, it really depends on your needs. I've got a Glock 36 that I carry during the week. I also have a P229 that I carry on the weekends. Lately, I've started carry the P229 during the week too. I really notice the extra weight on the Sig. When I carry it in a good pancake holster (not possible in my work clothes), it disappears. In my deep concealment shoulder holster, it isn't uncomfortable, but I know it's there.
If you get the Sig, get a good holster with it. Another perspective: I can comfortably carry my full sized M&P .40 with 15 rounds in a cheap Uncle Mike's IWB holster. The P229 with 12 rounds doesn't carry as comfortably in it. The extra weight really does make a difference.
So...either gun will serve you well. If you can shoot both accurately, go for whichever is going to carry better.