In my humble Opinion the best gun for ANY competition is one that you will carry to defend your life with. IPSC and IDPA both offer great opportunities to practice relatively practical scenarios with your carry weapon.. and the stress of competition can be an added training bonus.
Of course, IDPA does more to encourage this type of thinking, but that is a whole 'nuther ball of wax.
I suggest you take out your Glock 23 (or whatever) a few mags and a decent carry holster. You may not be as fancy as the guys with $2500 STI's and plastic "shelf" holsters, but you may develop skills that will save your life.
