I'll say this for Nero.
I like his outfit, his jacket, trousers and boots, so much so that I actually want a set for myself.
But in all fairness, Dante just wins the crown, his costume didn't do it for me in DMC 4 admitedly, too many belts, but his attitude was a nice return to form.
It'll always be like this for me.
Vergil > Dante > Nero.