To a close approximation, it doesn't matter. Rev engine, slip clutch to launch, versus slip clutch and immediately begin putting on the power.. no matter what,

To a close approximation, it doesn't matter. Rev engine, slip clutch to launch, versus slip clutch and immediately begin putting on the power.. no matter what, you need to engage the clutch and add throttle. The motor has so little mass it's not like it takes a long time to get it spinning before dumping the clutch on a low-torque motorcycle, and you can rev before the green. And regardless of what you're riding, you'll be across the intersection before most cars have even begun moving.