Have the Sigma 9 I have been on the fence about the SD, I like the rail and steel sights but the SD is such a small improvement over the Sigma I just dont see the point.
To me the trigger is fine heavy but constant breaks clean.
I have a Sigma and several M&P's. I am going to add an SD9 to the stable when I find the right deal (as in bargain). But because of snake charmer I suppose I will need an SW99 too.