It's easy to think that a more powerful bike that's been restricted would be quickest or best, but this isn't necessarily the case. There are a few variables to consider. What type of restrictor is being used? What are the characteristics of the engine?
A high revving engine that makes its torque at the top end of the RPM range is not going to respond well to restriction. Whereas a single or twin cylinder that has a lot of bottom end torque is likely to be just fine when it can be restricted using a throttle stop restrictor.
Restrictor kits are tailored to each motorcycle and differ in design and method of restriction. Some of the restriction methods are: