Is the M&P a reworked sigma? Why not they are both striker fired share similarities. The SD9 and 40 share the same similarities with the M&P and the sigma. The similarities are more toward the M&P. I own all 3, well 4 but that isn't the point. The Sd9 is a fine pistol in it's own right. M&P sights, extractor, a new more simple trigger design and for me a better size. Best "Bang" for the buck I've seen.