Banshees are cool if you have the time to take care of them and fix them when stuff goes wrong, but they are sort of a grenade on wheels, and when something goes wrong it's usually twice as expensive to repair as most quads because it's a twin cylinder. They do have a lot of quirks and shortcomings, but there's not much out there that's as fun to ride as a banshee. They just don't bring much to the table when it comes to suspension, handling, or any kind of technical/trail riding.
I'm not a fan of the 660 raptors myself, they're too tall and tippy, you spend all day trying to wrestle the thing so the front tires stay on the ground, and the dual carbs are a nightmare sometimes.
If you can any way afford it, any way at all, get a raptor 700. I'm not just saying that because I have one, I truly believe it's the most perfected, refined, all-around performing sport quad ever produced. Tons of power with smooth delivery, and tons more power available with basic bolt-ons, amazing suspension from the factory (the ones with the yfz-style shocks anyways), fuel injection so it starts the first time every time and never hesitates or bogs down, great ground clearance for a chain-driven quad, and the whole geometry and ergonomics of it are perfect. Low center of gravity, tons of room to move around and shift your weight when you need to, great weight balance, it has everything. I think yamaha may have screwed themselves with this one though, because they're going to have a real hard time improving it the next time they switch the models around.