"This thread has me thinking maybe for the purpose of a car gun or home defense gun a .357 just has too much muzzle flash & report."
Those are 2 of the 3 reasons I keep .38 spl +p loaded in my 686 for HD instead of full blown .357 Mag. The other being less tendency to shoot all the way through. Not only shooting all the way through a perp, but since I live in a fairly densely populated suburban area I am concerned with shooting all the way through my house into one of the neighbors' houses.
I figure that if I get a good solid hit, the perp won't know the difference whether it was a .38 +p or a .357 Mag that hit him.