Can we all take a minute and give it up for Spotify? 👏. Their casting experience is amazing! Instead of creating a separate instance of the app when you cast (IE. YouTube), it is the SAME app! That may not sound like a big deal but the biggest advantage is it let's you seamlessly move between your phone and the remote. Most importantly, all the functions still work with the remote. In contrast with the YouTube app which locks you into only being able to play/pause and does not give any options when you're using the remote after a cast.

TL;DR : Spotify casting >>> YouTube casting. More controls when casting then using remote

Edit: I'm dumb, you need to link your phone in the app😅. Thank you /u/ProgrammerPlus