My thoughts exactly... I've handled a few examples of both and the fit and finish on the Sigs were much nicer. Colt may have a proven track record... I'll give them that, but I haven't experienced any problems with mine.
Where did you get this information from? The last I heard, Sig uses the same steel all around as the Colt. They also MP test their bolts and barrels, they're not just marked. The Colt does ship with a full auto bolt carrier and an H buffer, but in reality, the Sig ends up having less recoil shooting many loads, thus the reason why JP uses reduced weight carriers and buffer systems. No rifle any civilian can buy without a tax stamp is milspec.

