I agree with the bigger, deeper bowl type diffusers, and think that ones with "fingers" help keep hair from getting blown around too much.

I have one of the pancake dryers, and find the diffuser next to useless as the holes are too big, and I'm afraid of getting my hair trapped inside the dryer. So that's a factor too.

Hot socks are about the only reasonable option if you're traveling, and relying on hotel dryers, but like the pancake dryers, they need to be kept away from direct contact with hair.
Peace,
Morgan

Baby Fine 3B, low porosity, normal density and elasticity
CGing since July 2008