Cassiopeia or Volibear

thats simple, are you a jungle main or mid?

Mid lane hyper carry if you have farm and protection.

Destroys other melee champs in duels and is super tanky. Only problem is its not easy to flip someone with your Q and if it is its going to cause a flash.

Having not PLAYED either champ, I can only give my experience of them from playing against them.

As stated, she's a mid laner. From what I've noticed, she starts out rather weak but gets almost exponentially stronger late-game. It's no shock at all, considering her passive. Her CC is decent, but when her ult is down, eh...

Again, it's been stated. This guy is a jungler. Volibear seems like he's much more even compared to Cass in damage and threat. Early game, he is one of those champs that I flash from pretty dang quick if there's any idea in my mind that he'll catch me. Late game, not so much. He's got great utility, as most junglers do, but his damage seems to taper off a bit. He's still really deadly, but certainly not as bad as Cass.

So, considering what I've experienced, do you want a late-game monster or something fairly balanced all through the game?