Well it really depends on what you are doing..
Around town i take the bolt evertime its more comfortable and easy to ride down low and etc.
But out on the track or highway riding(unless its a long ride) the rc51 is better it brakes better i have fully braided lines.
The suspension is better for track but kinda stiff for around town both set for my height and weight btw. Also it has alot more power and still alot of torque and its all very tractable coming out of a corner like the bolt but it just keeps pulling my only problem with it is it does not do really well under 3k rpm kinda ruff. especially at part throttle basicly it just feels like a ducati or 1125r.
They are both twins but very different bikes so i still like to ride both pretty much equally but in any kinda of race track or straight line the buell is going to suffer unless its a VERY tight track