+ 5 on the weight issue. It's a whole lot easier to move less weight around, especially if turns are involved.
As for power, you also need to think of displacement vs. time.
To use simple numbers, a 500 cc engine spinning 10,000 rpm is displacing as much as a 1000 cc engine spinning 5,000 rpm.
Your Busa engine tops out at 11,000 rpm.
The new Kawasaki 600 tops out at 16,000 rpm. (wow!)
The magic formula is
Horsepower = Torque x RPM divided by 5252
Small engines make less torque, but if you can spin them faster, they can make similar horsepower as big engines.
But torque, especially low end torque makes a bike fun to ride!