I am not a hard rider or one who one who likes "High G" turns so maybe I am not seeing some of the down side of a 21. All I can say based on my experience I like it fine.
I have the 21/17 combo on mine and I love them. Sure, I wish they could handle a little better in real slow speeds but I only ride those speeds less than 1% of the time. I haven't lowered it yet but I dont mind the ride that much that I need to.
anytime I get a chance to post a picture of it, I will.