The accepted champ is the 357/125 for several reasons, as Marshall and Sanow have shown several times. I generally agree with their criteria, i.e., not factoring in head shots, etc. Their data was based on actual street shootings, not ballistic geletin. While a 44 Special in the chest is probably nearly as good as anything else, the 357 hi-velocity loads bring one thing to the equation most others don't - hydrostatic shock. Mas Ayood has talked about this phenomenon for many years, based on autopsy results. Put your average 9mm/45/40/10mm (pick one) into the upper chest or shoulder of a bad guy, and he may or may not quit. But a fast 357 in the same place has often put the bad guy down quickly, and fatally as well. The 223 is good for the same reason.....the shock wave generated by the impact carries enough force to do things to tissue that slower bullets cannot. I remember one case where the baddie took one just below the left collarbone.......and promptly fell down and died. The initial supposition was that part of the bullet had severed the spinal cord, but the autopsy showed that the heart had been nearly blown apart by the impact. Impacts near/into the liver have also shown similar results. Less elastic tissue simply cannot withstand the force of the impact, and usually hemorrhages (sp?) causing a sudden and serious drop in blood pressure.
I have never seen anything from Dr. Fackler, et al that can discount this evidence, despite his protestations that penetration is everything. On a deer, give me a large hole, all the way through. On a bad guy give me a light, very fast bullet in the chest, though I'll probably keep shooting just to be sure he stays down for good. Sorry for the length of this response, but there IS a difference, and this is exactly why I carry a 357 with hot 125 grain hollowpoints!
BTW, I also own and carry 40S&W, 38Spl., 44Spl., and 45, but if the feces are headed for the rotating oscillator, I'll probably grab the 357 first.
PJ