Well, for IPSC I would look at something different. 1911's arent allowed in production class (which is where you want to be when first starting this type of shooting).
The 1911's that I see at all the matches tend to not run well. Some say its the magazines, some say its the reloads, but who cares! A jam is a jam!!
In production, you only have to meet minimum power factor. That translates into medium power 9mm or fairly low power .40. Glocks, XD's and CZ tend to dominate this class.
1911's tend to dominate the limited and open divisions. For competition, if you want to go with a 1911, I would look for one that is chambered in .40. Ammo will be cheaper, and you can make major power factor fairly easily. 9mm for major pwer factor is hard to do. Factory ammo wont make it, so reloading is your only option.
To sum it up: 9mm for production, 40 for limited/open. 1911 guns will not be allowed in production.
-George