other media players rely on directshow, which is one of VLC's weaknesses. it can't utilize it so is limited only to ffmpeg. meaning poor AVC performance and no dxva. another weakness is the interface. the good looking (wxwidgets) has crappy seeking and the skins are just terrible IMO. also far too many bugs but that can be expected with so many natively supported formats.
other players do use ffmpeg. the best (far less buggy than VLC, virtually no overhead, plays more formats than VLC eg real media) is mplayer