Not trying to argue with the idea that quad strength/power is very important in any VJ, but by which analysis do we come to the conclusion which muscle is, relatively speaking, the biggest contributor to vertical displacement? Judging from the thread adarq posted I see videos in which there is knee as well as hip flexion and extension to varying degrees. But that does not include any information on where the power is primarily coming from.
I think it would be wise to see it this way: Glutes and quads are both important for the VJ because they are the biggest and strongest muscles that are actively involved in it. Thus we should train both. I don't think it is actually of any importance, for a trainee, to know whether one or the other contributes more to the VJ.