What you notice is simply low frame rate video but there is another issue caused by frame time mismatch.
With a 75 Hz display and 23.976 fps video each frame wants to be displayed for 41.71 ms but Vsync is every 13.3 ms. This means that most frames are displayed for 40 ms but every ~8 frames one frame is displayed for 53.3 ms. This isn't too bad, only 33% longer, you might not notice it but it isn't ideal.
The effect is worse at 60 Hz, with half the frames displayed for 33.3 ms and the other half displayed for 50 ms, 50% longer. This is quite visible (to me at least) as uneven choppiness or judder, even worse than normal low frame rate video.
Smooth motion allows madVR to display every frame for exactly 41.71ms.
edit: with 29.970 fps video on your 75 Hz display you get a similar effect to 23.976 fps video on a 60 Hz display. Half the frames are displayed for 26.67 ms and the other half for 40 ms, 50% longer.