MKV 4:4:4 version requires high performance CPU for decoding. (probably at least 8 cores, e.g. Ryzen R7)
MP4 4:2:0 version can be H/W decoded with supported devices. (confirmed compatible on GTX960 and RX480)
However, for those who are using madVR, note that 4:2:0 stresses GPU more since chroma upscaling is required.
Thus, choose the appropriate version according to your replay environment and hardware compatibility.