I don't own a Kelly Dog but I think the Kelly Dog looks best when it fits in the middle (of thre three) holes. The CDC has four holes to adjust and I think it looks good in whichever hole happens to fit you. I wear mine in the smallest setting and I don't feel it changes the look of the bracelet.
I also read that the all-leather CDCs are bigger than the ones with metal, and some people who don't fit in regular CDCs can wear the all-leather ones.
I think it's best if you can actually try one on. Also there seems to be a difference in fit depending on the leather. My alligator CDC is the tightest, my lizard the best fitting, and Epsom the largest. The difference is tiny, but I can feel it. Each one also seems to stretch a little with wear, kind of molding to my wrist.