For several years, I used a M66 with a 2 1/2" barrel in IDPA. In IDPA at that time, the 625 ruled. However at the 99 Championship I finished second in the Marksman SSR division.
Today, IIRC, there are 2 revolver divisions. SSR, for regular speedloaded revolvers and ESR for guns useing moonclips. So you can choose your revolver based on your favorite style. A 625 is not needed to win.
I noticed on the S&W website that they have a special IDPA model now.