Talking peak hp, is almost meaningless when comparing similar power in two engines, as most riders cannot maintain the revs at the exact peak power point when riding. So a bike with a "peak" at say 21 hp., but that has a real spiky torque curve..looks like a steep sided volcano...will not appear to have "the power" that a motor which reaches say 20 hp., but which has a curve that looks like a rounded mound...not a perfect visual analogy..but still more or less accurate.

When you can average say 80% of peak power over say 2500 rpms, then you have much more "useable power" than a motor which will only average 50% of it's peak hp over the same rpm range..even though the spike at the top of the curve may be slightly higher in the second case....essentially the argument for a four stroke motor versus a 2 stroke motor. An expert rider may be able to use his peaky horsepower and be very competitive, but he will have to work much harder to do so, and has much less margin for error. He may have to keep the engine revving within a 500 - 1000 rpm range in order to have any advantage or just be equal. Of course where his peak is significantly higher(like a well done 250r motor)...then this argument fails. However a quick look at what is dominating the Pro and A class racing at the Nationals will help you understand this better.