I to was in this position not to long ago. after ALOT of research and hands on experience i had narrowed it down to the M&P 15-22 and the Sig 522 (both come with a lifetime warranty which can't be beat!) one thing that the Sig has over the Smith is that it uses the same magazines as an AR15-22 conversion kit. What does that mean? well that means instead of paying crazy prices a magazine you can get one for 14 dollars! (that is when everything calms down again). Also some of the M&P 15-22s have problems feeding the cheaper ammo. and if you watch any review online regarding the Sig most will say it functions flawlessly. Which so far for me it has done.