Also, they all offer free trials, so try them all.
Napster is 30m tracks, Pandora is between 30-40m tracks (per the Wikipedia link ZipperJJ provided)
I use Pandora Plus. I like the ability to make my own stations, and enjoy fiddling and fine-tuning them to my exact tastes. I usually listen to selected stations on shuffle according to my mood to get more variety. When I’m at work (in the library) if I hear a song I like I’ll check our catalog to see if we own any CDs by the artist, and if so I’ll grab them and rip them to my work computer, and later move them to one of my portable devices or a flash drive and take them home. Pandora sent me stats at the end of the year. I listened on average 1 hour and 20 minutes a day in 2017. For the price, I think it’s a great deal.
I haven’t been keeping up. I stopped using Pandora because the stations I had were getting repetitive. I may have to go back and give it a try.
Spotify premium, which is worth every cent.
I also love Discover Weekly.
mmm