.45acp +P's
One thing you might want to consider is the fact that Federal Hydra-shok stuff is +P. It is also the de facto standard most custom shops use when accurizing pistol barrels. It is, across just about every calibre, the most consistently excellent round I have ever come across, and I have yet to have feeding problems. (Even my somewhat picky Desert Eagle .44RemMag likes the .44 variant!)
Another round would be the fantastic stuff from Samson. If you've never heard of it, it's made by IMI, last time I checked. It's as completely flashless as it gets, and is pumped up to +P velocities.
As far as why, I wouldn't use it for game hunting. Although I wouldn't be TOTALLY naked with it around a marauding bear or something of that nature, there are much better calibres for the task (the aforementioned .44RemMag comes to mind rather quickly). But for the purposes of self defense, even the punks in Hollywood would have had a problem standing up to something that heavy and that fast. It might not have killed 'em, but get slapped enough, you start to cringe.
Platform is 1911. Colt or Les Baer or Kimber. 'Nuff said.