Cooler as in chill/relaxed Lucius. Bella has 0 chill. Bella is one hyper adult-child.

Cooler as in freaking awesome/badass Bellatrix by a long shot.

Calmer; refer to the above.

I'll go with the First meaning of Cooler, Because it means Chill, Rational, Reasonable, Sane, Mature, Relaxed, Charismatic, Sophisticated, Smooth and Suave.

Fair enough lol.

But I still like Bella better. ;P though Lucius is cool too.

Even though, Bellatrix is a Crazy, Tempermental, Childish, Insane, Psychopathic, Hot-Head, No Offence to you.

Yes, that stuff is actually why I like her lol. I enjoy crazy characters (like my favs are usually female villains half the time they are a bit nutty). I think the childishness and the immaturity gives Bellatrix a unique twist. 'Tis also what makes her such a fun and darkly humorous character.
That said, no offense taken.

Mine is Lucius Malfoy, Because He is Suave, Charismatic, Smooth-Talking, Chill, Sane, Mature, Persuasive and Sophisticated Male Villain. Sometimes I do like Suave, Persuasive, Charismatic, Smooth-Talking, Sympathetic, Sophisticated and Affable Male Villains.