The SD9 and SD40 are Smith & Wesson’s most recent polymer pistols. Their price places them squarely between the Sigma and M&P, which would be around $420 on the street.
The Sigma pistols are excellent guns for the money, but a few things have always been lacking. First off is the dreadful trigger pull, which is a long and uneven. They have plastic sights which are prone to breakage during adjustment, and the accessory rail is of proprietary design.
The SD pistols seem to address these issues. In fact, it appears that this model is simply an improved Sigma in many respects. What follows is a brief comparison.