For pure rigid bodies, indeed, both solvers have been validated against each other, but RBD is fundamentally formulated for large motion and large rotation and highly non linear solutions. That implies:
– Robust strategies for adaptive time stepping, whether it is using implicit or explicit time integration (as a matter of fact, for contact-dominated models, the MJ time stepping algorithm is the recommended method, and is implicit!)
– Dedicated techniques to deal with very large rotation increments over one step
– High fidelity: Consistent tangent matrices, energy conservative integration schemes, Lagrange multipliers formulation for contact, full non linear formulation of equations of motion.
– Allows for loads dependent on model state
– Solver tuned for relatively small number of degrees of freedom but large number of time steps.