On my last range outing to shoot my new Beretta 92 FS Compact, a friend joined me with his newly purchased Sig 226. This was the Mk-25 version as adopted bu the US Navy Special Warfare Group. Not having owned or shot a Sig in years, after shooting it I could understand why the Navy chose this pistol. It was an obviously well built pistol that operated very smoothly. The P226 was in serious competition with the Beretta 92 in our service pistol trials in the mid 80s. It is used alongside the Beretta as the M11 and now the Mk-25. Shoot one and you'll see why.
From what I learned one of the main reasons it lost out was the cost, obviously the SIG was a bit too pricey for the US govt to pay. But there are several special forces that adopted both the mk25 and mk11 as well.