It is WAY smoother to ride with the track style, releasing the clutch every gear. I allways ride like that, at the track or traffic or off road. Riding like that you are allways on the right gear and right rpm for the curve/situation. And you are then using the engine as rear brake. It is WAY smoother.
And smooth is fast.
At the track you actually trail the brakes (front brake) all the way to the apex and down shift at the same time. Blipping the throttle while downshifts for smooth shifts. If you use the track method, you need to blip while down shifts, or you get a lot of CLUNCKS and eventually break your tranny.
With the track method you allways have the engine connected to the ground, either engine braking or accelerating. RPM and gear matched to the situation.