The best for featured rock
I have led pitches on friends' BD stoppers as well as my Wallnuts. My general impression is that the complex shape of the Wallnuts (shallow cutouts on the wide sides and a slightly more pronounced curve) sometimes give you a better placement. I climb on featured, East Coast rock, and I especially notice that a small crystal or bump will sometimes seat nicely in the cutout and give you extra confidence that the piece won't walk. If you want the best, Wallnuts are it. The question is whether you feel the need for that slim advantage over cheaper options like the standard BD stoppers.