The chambered choice begs the question. The only semi-auto I would carry with one in the chamber is one that has a hammer and a firing pin block safety.
The majority of accidental discharges with semi-autos seem to occur with striker fired pistols that rely upon trigger pull distance to prevent accidental firing.
There is no difference between a hammer fired pistol with a firing pin block safety and a striker fired pistol. Both of them will discharge when the trigger is pulled fully to the rear - which is the cause of the vast majority of negligent discharges. Striker fired pistols also have internal safeties designed to keep the gun from firing unless the trigger is pulled fully to the rear.
For example, the gun that I carry:
http://www.gunblast.com/Taurus-PT145.htm
The Millennium Pro has several built-in safety features. It is of a double action striker fired design, and has an internal firing pin block that prevents the gun from firing unless the trigger is pulled. This is the primary safety, and all that is necessary. However, in addition to that, the gun has a manual thumb safety that is easily accessible to a right-handed shooter, if he so chooses to engage that safety mechanism.
BTW, for the poll - PT-145 loaded 10+1 safety off in Fobus paddle holster.