It depends a lot on the kind of feel you like in the riser. My Kanatis are both dymondwood and I love it. As Jason said, it adds about a quarter pound for a total of about a pound and a quarter vs. one pound with actionwood. My son's Kanati has an actionwood riser and it is one of the best shooting bows I have ever shot.
I don't think you could go wrong with either. I think either of the laminates are more stable than natural woods and I think they are just as good looking. If you like the gray, take a look at the bow Jason is featuring on his website with the gray dymondwood riser and camo limbs with amberboo core. It is almost as nice as my walnut dymondwood, camo limb with amberboo core Kanati...almost.
I spent about an hour and a half shooting both Kanatis tonight. I was fine tuning the nocks on the new one to get it dialed in to shoot to the same point as the 46# with 1916's. At 9.3 grains per pound of draw, the 52# Kanati just flat smokes these arrows! At fifteen yards, I can't even see them fly. I just release and they are on the target. I always thought the 46# was fast for its draw weight, but this new one is scary fast! I have to get back to over 20 yards to see the arrows in flight.
Sorry for the hijack, but I am just so pumped about this new Kanati!