Between Moon Cass and Moon Varian, who do you think would win in a fight?
Depends on time they have to learn their powers. Cass took to it so naturally, and Varian likes to study to understand. If this were "poof! Both holding the Moonstone. Now fight!" Cass for SURE.
Had time to learn their powers and prep? It'd be a much closer fight. I lean towards Varian, because he was able to do a number on Cass in PEEV just by studying the rocks. Imagine if he had the actual Moonstone to work with! But Cass is a trained martial expert. She lands a couple blows--even just one strategic one--and he's down. (Not to mention he passes out at the sight of blood).
I firmly believe that, given time, resources, and information on his enemy, Varian could likely take on anyone. He's a glass canon, though. He can hit hard, be clever, make machines and chemical solutions.
Boy can't take a hit, though. I mean... in Nothing Left to Lose, he was quite literally beaten with a rock and kept singing. The blood thing, though? If Cass actually tried to cut him? I'm just not sure. It's a huge weakness that Cass knows about!
If he could get over that, I think Varian, but not easily.