In my limited experience, I've found the .30 to be especially accurate.
Shooting my Commercial .30 with Winchester white-box FMJ, I had no
problem getting it to average 1.3" off the bench at 25 yards for several
5-shot groups. After rebarreling with a 6" commercial barrel, my better handloads averaged 1.245" for 5 five-shot groups at 25 yards.
My limited testing with a pristine DWM in 9mm (4" barrel) showed that it couldn't begin to approach that level of accuracy, shooting groups of several inches at 25 yards with Winchester white-box 9mm FMJ and a single handload using Win. 115 gr. JHP's (that shot with match accuracy in a bullseye-accurized Beretta 92 set up for NRA competition.) However,
that's just one specimen, and I never did attempt to develop a load specifically for that pistol, which might have shrunk groups some. The 9mm sure is a lot less finicky and easier to feed, in my experience, and components are everywhere. I search hard for every piece of .30 brass that turns up missing on the range, while with the 9mm, it's no biggie if a few go astray. I especially like the idea of getting a shooter 9mm Artillery -- that'd be my choice, if, like in "Highlander," "There can be only one!"
John