What is the difference between optical flow and a VNTrajectoryRequest? Would tracking a trajectory of an object benefit from a work flow that used both?
The trajectory request is especially developed to track objects on a trajectory meaning not any kind of zig zag path. Optical flow will detect any motion without the constraint of a trajectory
So if you want to track a ball been thrown, you will get better results with the trajectory request.
If you want to see if something moved in for instance security camera footage then you use optical flow.