You could consider using a model 646, for ICORE. It has the titanium cylinder rather than the standard stainless cylinder. Supposedly the ti cylinder makes for quicker transitions. Unfortunately the 646 is only available with a 4" barrel, so you have to go with the shorter barrel length, and the corresponding shorter sight radius. The good news, is the fact that S&W now has the ti cylinder available for the model 625. A shooting buddy of mine was having a problem with peening of the cylinder stop notches on his 625 so he sent the 625 back to S&W for repair (2nd repair for the same problem). Somehow he found out about the availability of the ti cylinder for the 625, so he paid for the upgraded cylinder. According to him, the ti cylinder will be less prone to the problem with the notches.
Both my son and I use a model 610 for Icore. Mine has the 5" barrel, while his has the 6.5" barrel. He likes the extra weight of the longer barrel for absorbing some of the recoil, even though we are only shooting a 120 power factor. He feels that the longer sight radius, and time saved in getting back on target with the heavier barrel outweighs the slower transition time. All I know is that he kicks my butt at every match.