Crash.net comments stating that former 500cc World Champion Wayne Gardner has said Ben Spies' title-winning Yamaha YZF-R1 is the most difficult bike to ride on the WSB grid (also tested a Ducati, Suzuki, BMW, Honda and Kawasaki)! "

I have not seen that quote from a more reliable source yet though. I'm guessing it's just the way he preferred it because he's a bigger guy for a motorcycle racer, and probably not as easy to toss around compared to the others.