YMusic is specific designed to work with music so the player, loading times etc are better. in NewPipe you first need to open a video, click play (or tab and hold to play), select play in background etc.. and also create your own playlists. in YMusic you click just on a song you like and boom, it plays. also it can download quickly the music and also recommend automatic new music etc.

YMusic is just way better for music. you can even login with your yt account and use your music playlists etc. from computer.