In "practical" 3-gun, or multi-gun competition, I suspect the number of .45s will depend on whether the rules give an advantage to capacity, or not. USPSA's Heavy Metal division specifies a bullet of at least .44 caliber, and mag capacity of no more than eight, so you'll probably see nothing but .45s, there. In the other divisions, everyone is shooting the pistols that they use in those same divisions for pistol-only competition. I shoot Limited 10 with a single stack .45, so when I shot Multi-gun Nationals, I used the same gun in Limited division, as I thought it was important to use the gun, and strategies with which I was familiar.