PipePipe is the most reliable for Youtube (well aside from Seal or other methods of using YTDL on Android), and Tubular is what I prefer for Bandcamp/Soundcloud/Youtube music videos, but the aggressive caching on Metrolist is what sets it apart for me, comes in handy while saving data whenever I forget to download a song.

Also, if you use KISS Launcher, this is the only thing that can actually read Youtube search URLs, and having a YT Music-specific search app saves a lot of time.