MP4 is the world's default video: the file that plays before anyone has to think about it. It was born in 2001, the MPEG standards group, built on Apple's QuickTime design, and its real weak spot is very little day to day: as a container its quality depends on the codec inside.
WMA is Windows' old house band: big in the early 2000s, mostly retired now. Windows Media Audio, in several variants including a rarely-sighted lossless one. That makes it the right destination when what you need is keeping aging Windows Media software and old archives happy.