Leviathan looked blazing fast, and I voted for it.
So, Behemoth it is.
In regards to the hyper coaster vs. giga coaster debate, B&M does not differentiate between the two and honestly Leviathan didn't feel significantly different from any of the other B&M hyper coasters (unlike with Intamin rides...Millennium Force and Intimidator 305 are very different from Ride of Steel and Bizarro). It was just bigger, faster, and with a more interesting layout. Also, for the record, here is my ranking of the B&M hyper coasters I've been on (six total, with two new ones (Raging Bull and Diamondback) planned for this year):
Nitro (Six Flags Great Adventure)Leviathan (Canada's Wonderland)Intimidator (Carowinds)Apollo's Chariot (Busch Gardens Williamsburg)Behemoth (Canada's Wonderland)Goliath (La Ronde)
Keep in mind all of these are still top tier coasters. The top four all make my top ten list, and even Goliath is in my top 30 (out of over 250 coasters).
Oh, and James, Leviathan is nothing like Intimidator 305 (which is a very overrated ride in my opinion). It is somewhat like Millennium Force (not sure if you've ridden that), but still feels like a B&M hyper.