Well, use neither of those. I use a flat diamond stone with the wooden base removed. Mine is six inches long. I want one 8-9 inches as I bought the one I have to sharpen my folder, which was the only knife I had at the time. I also have a moderate-sized fixed-blade, and have alway been able to put a better edge on with a stone longer than the blade.
My reason for choosing the diamond over ceramic was because I travel quite a bit, and do a lot of time in the field. Diamond stones, being metalic, can take more whacking around. Not to say ceramics are as fragile as they sound.
I bought a set of Croc Sticks, couldn`t figure how to make`em work at the time, so traded them in the nest day for a Lansky Arkansas. Anybody still use one of those?
Main thing was I couldn`t figure how you are supposed to sharpen on a stick that`s, well, sticking up in the air at an angle. Still don`t get it. At a gun show, a fellow knife enthusiast who`s table I visited had a 5" Spyderco ceramic sharpner, I think it was a sharpmaker, vaguely oval in cross-section. He used it as a flat stone, and in two strokes had a good edge back on my knife, which is sharpened, and used, with great frequency. I think in this case he was more straightening the edge then removing material and "sharpening" it. Still, it did the job awful quick. `Takes a couple passes on the diamond.
Note that there was a chip knocked out of the corner, though it did not impair function. Someday I may try a ceramic number like this.