As an IDPA novice, I tend to shoot for familiarity with my equipment and the scenario. At my last shoot, a lot of shooters were using M&P9Ls and other competition style set-ups (OWB holsters, cover vests). On the other hand, I was slower (okay a lot slower), but used my everyday carry rig (IWB and a shirt).
I would not worry too much about purposing a gun for IDPA--unless you're really in to IDPA shooting, I'd worry about more primary considerations, like concealability, familiarity, and comfort.
IDPA is great for familiarizing yourself with shooting on the move, moving to cover, etc. While not true of all shooters, I've seen some people so pressed for speed that they'd draw and just rip off rounds, occasionally missing the target entirely, but making good time. As you've heard. Speed is fine, but Accuracy is final.
Just my two cents.
