AVI and Matroska are just container formats. What makes a difference is how the contents are encoded. Most MKVs I've seen use the Theora video codec which is more resource-intensive than DivX (MPEG4) ...
If you have MKV files and you want to play them on your computer, you must have an app that supports the MKV format. That is why you can download these MKV player apps for Windows 11 and Windows 10 ...