I have the Sigma (with trigger spring replacement) and am Currently trying to justify gittin' the SD. If'n the M&Ps are that much better than both, I don't c the need to have a Sigma and an SD. Perfectly happy with Siggy.
Somebody posted that they do what they are made for but still insisted that the M&P was better (for S.D.) but if the Sigma doesn't have durability issues or malfunctions, what's wrong with leaning on it for S.D?!?