i don't know about best, but my kid loves her Reisport buckle grips. My younger one uses the Reisport velcro and likes them as well. We bought them both drybands rather than wristbands and they rave about those!
My DD likes US Glove (Hot Shot Leather Cuff Single Buckle) but she likes a narrow style so she can feel the bar. She has several teammates that use Reisport, but mine personally finds them too thick/wide (she tried but couldn't get comfortable with them). Another popular brand is Ten.0.