I'd like to suggest using your carry pistol, assuming you carry something bigger than a BUG. IDPA is a good opportunity to practice using your real-world gear. Now, if you don't normally carry strong-side IWB or OWB, it doesn't make as much sense, but you can still get a belt holster and compete with your carry piece. It will be more opportunity to perform presentations, malfunction clearances, shooting and moving, all under the pressure of the timer.
I've been shooing IDPA since 2000 or so and I've been a safety officer for most of that time and was a match director for a bit. The intent of the sport is to shoot with your actual carry gear, with certain restrictions for safety and nodding to the fact that it is a game. I'm never going to win national titles, so I use matches to practice with my real gear. If I was a top-ranked competitor, then I'd go for whatever edge I could get in guns and gear, even if it was not what I carried.
Just my opinion.