Bullets "stop" people and game in all sorts of different ways for all sorts of different reasons. Fast and light has a completely different set of stopping properties vs. slow and heavy. Look at the .357 vs. the .45acp. One could argue that they are the best going for SD yet they get the job done completely different ways. Same with rifle rounds like the .30-30 vs. .243, etc etc. The same can be said between 125gr vs. 158gr .357M. One does a better job stopping in certain ways, the other in other ways. Which is better? Doubt we'll ever have enough information to make a good judgment between the 2.
But certain principles don't change. Fast and light beats slow and light. Fast and heavy beats slow and heavy. That's why the .357M beats the .38sp and the 9mm. It's why the .44M beats the .357M, etc etc. Now bullets have changed tremendously over the years. Go read "Sixguns" by Keith and you'll see he had little time for the .38sp. Of coarse he was using mostly cast lead and with those his heavier, wider .44sp. and.45C loads did better, So did the much faster .357M. Kinda a duh don't you think. I often wonder what his findings would of been with modern bullets and loads. The .38sp never would of over taken the .357, 44sp and .45C but it may of moved the .38sp into "acceptable" range instead of the scrap pile.
As for this:
I would bet you could put a modern day 9mm bullet against the old 37mag for one stop shots and you could hardly measure the difference.
You may be right. But what if we take modern day 9mm vs. modern day .357? Gotta keep apples to apples don't we? But never the less I generally feel you are right and why I find most "which cartridge" threads bunk. Still, properties don't change and on questionable hits I'll take a heavier and faster hit over a slower and lighter hit. You guarantee me ONE shot to the brain pan or heart and I'll take about handgun ever made. Good luck on that guarantee though.