i have yet to see a 660 or a 700 run worth a shit. they are a fuckin joke at the hillclimbs i know that much.
i ran a bunch of them in the sand on my 450(exhaust, cam mod, intake) and i never once got close to being beat.. then again i am a way above average rider.
im sure those bikes run hard, once you dump an assload of money into them.. otherwise, im not impressed.
i really hate to compare 4 strokes to banshees. there are entirely too many variables that come into play. tires, tire pressure, rider weight, rider ability, riding terrain etc..
the list could go on forever. its really impossible to even compare the two until all variables are the same for both.