After kicking this around for a bit i got together today with a friend of mine and we went out shooting at the range. I brought along my hi-point 40 s&w, and my Bersa Thunder 380. He brought his original 1911 and a Taurus .357 magnum.
I mentioned to him about this debate and he said hey, they rent the hi-point .45 acp here and the frames are near identical given the small caliber difference, lest test them...cool!
Anyway we shot both hallow points and flat nosed fmj 40(wad cutter style?) and round 45acp and compared the difference. The kick was a slightly more in the 40 S&W...but ever so slightly with the fmj....due to flat nose? then the hallow points the 45 kicked harder?
We used max load Winchester fmj in Winchester and hallow points were Hornady (since he had Hornady we matched a box in 40 s&w).
So i said hey lets get some reloads, they are round nose and save the good ones for home.
So we tried the reloads...and wow no difference.
Interestingly enough we broke for home and set up some clay for ballistics.
The forty Winchester had same penetration, from the 40 s&w more damage (thinking the flat nose).
So we tried the hallow point and we had slightly more damage from the 45 acp and more penetration from the 40 S&W.
Then said what the heck tried the factory loads and had 3 1/2" more penetration from the 40 s&W about 12 3/4" vs about 9 1/4" 45acp.