Horsepower is horepower. Dynos don't lie. If a Banhee has more horepower, it's more powerful... plain and simple. The 450 just happens to have the best power to weight ratio of any 4 stroke yet so we're kinda blown away by it. After all, we're used to the 400ex . We all know the 450 was designed WAY better so of course it's going to blow away a Banshee in MX. Which one will win in a drag? That all depends on circumstances (length, traction, gearing, blah, blah, blah). Which bike is better? That depends on what you want. If you're a modder, then the Banshee is definately for you because it's customizable beyond anything else. If you just want something to hop on, be reliable, and haul ass on out-of-the-box, get the 450.
In short, to each his own. Quit bashing each other!