Vinyl is CAV (constant angular velocity) which means the speed is constant. When it comes to CAV you need to have as precise as possible constant rotation speed. This is why belt drive can be used, which also helps eliminating the vibrations from the motor drive.
Digital formats CD, DVD, SACD are CLV (constant linear velocity) which means the rotation constantly changes preserving the linear speed constant. It is controlled by a servo system. Earlier CD players used slow and noisy analog servo systems, the newer ones use super-fast digital servos. This contributes to reduced jitter induced by the servo system.
This said, it is strange to me that someone would design a belt driven CD transport since it will not be capable of fast and accurate speed changes needed for proper speed control.
So I vote for direct drive.