I tend to like smaller hand-held sized stones. But I prefer ones on the narrower end of the spectrum as well. I have one coticule that I feel has the best dimensions out of all of them. It is roughly 8.5"x1.5"; A nice length for a long stroke, but fairly narrow.
Another size I feel is nice is a 6"x2". Hey, you don't even need a rectangular one either. The coticule in my avatar that is closest to the bottom is a great sized hone IMO. It kind of has the best of both worlds with a wider end and a narrow end. :D
I personally believe that there is no "perfect size". You just kind of get used to the size you have and learn how to make the most of it. :rofl2: Those last two sentences can surely be applied to more than just the size of hones......