IDK which is the best alternative... I have a couple installed because every once in a while, YouTube will change something that temporarily breaks some or all 3rd party apps... Having alternatives give more options for having one that either didn't break or is updated faster than the others...
Having said that, I have Metro Tube pinned to my start screen... It lets me log into my account, so I can see "adult" videos (like the Fallout 4 S.P.E.C.I.A.L. Videos that are tagged as age restricted for some reason and require you to be logged in). It also lets me download the videos so I can watch them later.