click to show spoiler
Young, skilled, feul injected blade, devil arm, good gun, nice combos, yamato
Experienced, 5 different styles (yes, five. Wehn dante acquires Yamato in the fight against the savior, he gains a fifth style. Dark Slayer, i think), more than one ranged and melee weapon
However, in badassery, i think both are equal. Both can dish out insults like nobody's business
"Isn't that a little harsh? Killing me for the way I t-t-t-t-t-t-t-talk?"- Nero to Agnus
And the whole scene with Agnus and Dante in the opera house proves Dante is the better man.
but all in all i think that both are equal. Dante is slightly better, but nero could possibly surpass him with time.