I'm going to go with Spegel boot grips, with Ahrends boot grips a close second.

Spegel's get the nod because I really like the palm swell they use. I don't have big hands and most finger-groove grips I've tried spread my fingers too far apart for a good grip; the grooves on Spegel's grips fit my hand well and aren't even noticed. I only have them on my 642, but someday I want to try a set for my K-frames.

Ahrends boot grips fit my hand well and are available without finger grooves. I also like the tung oil finish; smooth without being slick.