I think it would be very close!!!

I think Severus has more knowledge than her, probably a little more powerful too.

Very colse, but when it comes down to it Bellatrix is more skillful

Snape keeps his cool, while Bella does a lot of things spontaneously, and that gives Snape the advantage.

Snape would totally dominate

Bellatrix would pwn

Easily in my opinion.

Snape because he was smarter, knew more spells, and was less impulsive (he thought about his actions more, thereby making less mistakes). I believe Bellatrix was driven by pure hatred and maybe a mental disorder. Snape is smart...smart enough to fool Voldemort..when no other death eater(or fake death eater) could.

Bellatrix of course...

Bellatrix is gifted and very skillful and really crazy