NONE OF THE ABOVE
The ND To waypoint prediction is based on the (real-time ) bearing between the aircraft and the To waypoint, whereas the MCDU predictions are based on the FPLN trajectory, i.e active leg
That doesn't explain why theres a difference when u are direct to a waypoint (which the almost always is) which is what was originally asked. Pretty sure it's because ND assumes the current GS remains the same until the waypoint is reached and MCDU uses predicted figures based on input winds & planned changes in speed. Which is what has been said above.