I prefer H&ks to Sigs generally, although both are fantastic premium quality pistols. I think you should be looking at the HK45 instead of the USP.45. Ergos are far superior to both the USP .45 and the P220, IMHO. At a mag capacity of 10 rounds you lose 2 to the 12 round USP.45, but still have two more than the 8 round mags of the P220. It has a full-length light rail up front (whereas the USP requires an adapter) and it is lighter than the P220. You can carry it cocked and locked or DA/SA. You can't go wrong with any of these guns being discussed, but IMHO the HK45 is the best.