Michael R asks a quite common question as people will always think that one type of bike is better at Moto Gymkhana than another. You only have to walk down pitlane at a Japanese Moto Gymkhana competition to be amazed at the enormous range of bikes that are being used and if any one type of bike was better at Moto Gymkhana then you would expect that type to be in the majority. This may be slightly true for the NSR250R, but that bike has deep cultural significance in Japan so you would expect to see quite a few of them.
Each type of bike will have advantages and disadvantages, but the course designer usually takes these differences into account so that the overall time is entirely down to the skill of the rider.
The best bike FOR Moto Gymkhana is the one you are riding IN Moto Gymkhana!
Dedicated to the wonderful sport of Moto Gymkhana