It's all about the tires you have, what gear you launch in, the rider weight and how good the rider can shift and what your suspension is and set to.
I would race KTM 525 on dirt with stock tires and 5psi in them and launch in 2nd and stay with him spinning up to 4th gear. He has race tires and bigger motor. If I had better tires I would have killed him. I launch in 2nd because launching in 1st slows you down and is more of a delay and you have more powerband climb time in 2nd.
Same goes for when I raced a stock Honda 450r on the same road, I would beat them in top end once I stop spinning and sometime I would even out launch them off the get go if I launched right and sat on the back for traction and slammed through the gears just right.
Just my 2 cents to help give you perspective.