Yeah as MegaGeeza said, certain racers specialize in one or two speeds.
Sinus1 was the first to get to level 101 and he did that playing Flash speed almost exclusively, same with Slowtrain and Texasalex.

The thing is, that different opportunities to do barrel rolls on the same track appear at different speeds.
I think it is Venom and Flash speeds are the ones you can do the most at.

Many a good Phantom speed pilot has had their butt kicked when dipping their toe in a Venom/Flash race and coming up against one of these specialists.

You just have to see some of the results that have happened during the HD CUP.