I like the 4" simply because it is the length I carried while at my first Police Department in 1985...(Yes we were just changing over to semi-auto's. We were authorized to carry 1911 types.)

I just shot my 586 today with my wife (She shot it as well.) Smooth as silk trigger very accurate. We were at my buddies private range and shooting at 25 yards, at two foot by 10 inch metal targets..it hit them every time smack in the center.

The only difference is a slight increase in weight and a little less muzzle flip...I didn't ask if you were thinking about carrying concealed?