Although this is an old topic, I can confirm, what Madshi said about 25 fps movie content. You can choose whatever video codec and combine with or without Dynamic Refresh Rate in MP settings and this will for sure show heavy judder/stuttering with the internal MP video player. Using ffdshow with MADvr with an external player and you get nice a smooth playback. So for me there is no alternative, than using an external video player in MP. Works with MPC-HC, Zoom Player etc.
This is a problem both in MP version 1.3/1.4/1.5
Which version of Windows etc. are you using ? - I don't have any problems with 25 fps content on a 50 Hz display using MP + EVR.