Not the debate you're thinking of! I don't care about shooting ballistic gel, rather, I care about shooting steel knock-down targets with a sub-machine gun. I have a gun I'm trying to set up for a subgun match. I can use any caliber .380 or larger in the competition, and I can configure my particular gun in 9mm or 45ACP.
I was originally all in for the 9mm setup, but many of the shots need to be made as singles where, in an open-bolt SMG, neither caliber has a distinct advantage. Other targets are setup where they take 3-4 hits from 9mm on F/A to knock down. I think .45 could do this faster and maybe save me a mag change by the end of said targets.
In your opinion or experience, is it more useful to have the burst-controllability of the 9, or the ability to better slap down targets (that require multiple hits) with the .45?