My opinion is impossible if they can drive well. A stock yfz450 w/o the baffle killed my shee with basic bolt ons. YFZ's are a beast. Mod for mod, 450's will beat a banshee. But if you go beyond just the basic bolt ons, the banshee takes the lead and it's cheaper to do.
Get a shee, port it and mod it according to the port job to really bring out that port job and you will be fine. That's my 2 cents. Oh yeah, learn to drive it. It took me a while.