Why do you consider the 10mm more flexible? More ammo choices, or some inherent ballistic qualities?
Actually not so much ammo choices, as the wide variety of bullet weights available for handloading. I've handloaded a variety of bullets weighing from 135gr to 205gr all with superior ballistics to the .45ACP and slightly better than the 400CorBon. The maximum reccomended bullet weight for the 400Corbon is 165gr. The 10mm has a bit more snap than the .45ACP. More like firing a .41 Magnum.
Also most semi auto handguns chambered for 10mm can also safely fire the .40SW using the same barrel (there are exceptions to this rule), and can be rebarrelled easily to handle the .357 Sig.
Revolvers chambered for 10mm (primarilly the S&W 610) can handle .40SW right out of the box. This is not the case with the Ruger Buckeye Special Blackhawk which depends on casing length for proper headspacing.