Well, i prefer Nero, since i like his DB, but if i`m playing Dante, then...
FOr bosses i tend to use Gilgamesh and Lucifer with Swordmaster or Trickster style, Rebellion too sometimes, and while i cant get near a boss, Echidna for eexample - Ebony and Ivory(charged), otherwise - i just use Rebellion and Ebony and Ivory with Swordmaster style for the lesser demons. Pandora`s a kick ass DA, but takes quite long to shoot... and is quite unprecise..for enemies tend to run sideways...
Mainly i stick to one style and love it. Hate changing styles...