Are some surfaces better than others for barefoot runners?
Any surface that isn’t covered in glass is better than any surface that is. Past that point, the best type of surface is variety. That sounds like a cop out, but I feel it’s true.
Barefoot running is experienced with sensory perception and the best way to promote that is through varying the surfaces you run on. Packed dirt feels different than pavement, which feels different than asphalt, which feels much different than woodchips.
Most people try to steer clear of gravel, despite its ability to short track you towards landing lightly on your feet. I can’t say I blame them though.
The best surface to receive feedback on is a smooth hard surface. Grass and dirt can be very forgiving of bad form. A hard surface provides better and more consistent feedback on your form.

I learned on a soccer field: grass and dirt with grass having the edge. Of course I was a little naive back then and have since stayed on harder surfaces.
Rough old cracked asphalt on steep hills will learn ya right quick, too.
I think running on asphalt is much better rough pavement :)
I ran on the hottest days on both concrete and asphalt with no problem this summer. Then I ran on the track at the Univ of Akron and got blisters. The track absorbed more heat than the black asphalt!