Often times, basketball players have used one-leg jumping their whole life. It's just a much more natural movement because it's used every single time someone goes for a layup. On the other hand, volleyball players are often used to two-foot jumping because it is the most common way to jump when trying to block or spike. So, if you have all the suppositions to be a great two-foot jumper, but you get barely of the ground this way, it's probably because of a lack of technique.

Muscular strength and explosiveness must be developed in conjunction with flexibility if the athlete is to maximize the jumping ability and reduce the risk of injury to structures such as the Achilles tendon and knee ligaments. Flexibility, when achieved through focused stretching programs, will serve to increase the range of motion in the joints essential to jumping: the ankles, knees, and hips. A common muscular deficiency that plagues athletes who require well-developed leaping ability is a lack of flexibility and resultant strength imbalance between the quadriceps (thigh) muscles and the hamstrings, the pair of muscles responsible for the flexion and the extension of the knee. Proper stretching will assist the athlete in the maintenance of an approximate 3:2 ratio in the relative strength of the quadriceps to the hamstring. When there is a significant deviation from that proportion, the knee and the muscles themselves are at greater risk of injury.
For one-footed jumpers, the ball is generally transferred to the non-dominant hand just before or upon take-off; for two-footers, this transfer is often delayed for milliseconds as both hands control the ball to prevent dropping it. Once airborne, the dunker generally transfers the ball from non-dominant to dominant hand beneath a raised leg. Finally, the ball is brought upwards by the dominant hand and slammed through the rim.
The method described above is the most common and simplest way to measure one's vertical jump, but other more scientifically accurate methods have been devised. A pressure pad can be used to measure the time it takes for an athlete to complete a jump, and then using a kinematics equation (h = g × t2/8),[4] the computer can calculate his or her vertical jump based on the time in the air.