A lot goes into these types xxx vs yyy threads.

Barrel length is huge as is bullet weight. The big ammo mfg's ammo is anemic at best. I know Ed has done extensive testing over the last couple of years that I followed on this website with the 38spl loads and now the 9mm.

At the end of the day IMHO:
short bbl's (3" or less) & light bullets ='s 9mm
short bbl's (3" or less) & heavy bullets ='s 38spl
4"/5" bbl's & light bullets ='s 9mm
4"/5" bbl's & heavy bullets ='s 38spl
6" & longer bbl's ='s the playing field starts to level with the edge going to the 9mm with lighter bullets
10" bbl's ='s doesn't matter with lighter bullets and anything over 147gr the 38spl really shines.

I have short bbl's 9mm's and use 124gr bullets
I have short bbl'd 38spl's and use 158gr/170gr bullets

I've done a little reloading/testing with both calibers over the decades. Bought my 1st chronograph in 1990, started casting bullets in 1985 & swaging bullets in 1990.

Started reloading the 38spl/357's in 1985. Since then I've tested bullets weighing 90gr to 200gr (lead & jacketed) in 1 7/8", 2, 21/2", 3", 4", 6", 8", 10" bbl's. I have no idea how many different powders I've used/tested, 20+ is being conservative.

Started reloading the 9mm in 1991/1992??? We would re-fit our 1911 38super race guns with 6" bbl'd 9mm bbl's. We used the extra length (38super 5"/9mm 6") of the bbl to get more speed out of the 158gr bullets we were using in the 9mm back then. Since then I've tested bullets weighing 90gr to 158gr in 3.2", 4", 5", 6", 10" bbl's with the same 20+ powders.

This doesn't make me an expert by any means. I'm just saying I've done a little testing in a bunch of different firearms/bullets/powders for over 25+ years. What little I've learned I listed above.