I shoot my 1911 at IDPA, but I know:
*the safety is going to be a little slower than pulling a glock.
*It only holds 9 rounds as opposed to 11, which sometimes means an extra reload
*Ammo is more expensive than shooting 9mm
Having said that, I also feel it is safer on my hip, .45 is a superior round in practical use, and most gun fights won't exceed a a few rounds and for those reasons it is what I would carry if I was allowed. I also usually use an IWB holster, which is slower again, but it is what I would use if ccw were permitted. As has been said, I think it depends on what your goals are. I know it is not "combat" training, but I do try to use the mindset of what would I use in real life. Also, I love shooting a 1911 and don't enjoy shooting 9mm as much, and at the end of the day, fun is the name of the game. If my goal was strictly time I would use a 9mm single action.