I think the most discussed thing in this area is the handle of juggling clubs. Compare Beard beach, to henry delphin, to PX3, to bare spiral wrapped, to taped (and all the variants of tape).
Stage balls also come in a variety of textures.
I would say it is fairly well explored, but in those, very restricted areas.
I remember speaking to Davide at PLAY about this. Every juggler has their own opinion of what is best, it seems. Some want grip, some want slippery, etc.