I've owned (and own) a few canvas micarta handled knives and only handled some carbon fibre handled knives.
I'm thinking the gripability aspects of these materials is dependent upon how they are finished.
Media blasted or rough sanding seems to yield good results.
Unfortunately, most carbon fibre seems to be finished with some kind of clear coat (usually thick) that results in a slick surface IMO. Spyderco's recent Military had highly gripable carbon fibre, though.
Perhaps one of the makers will answer in with more difinitive answers.