Carsten asked some questions in a comment regarding Deezer:

Does the Deezer catalog also contain Die ???, Sherlock Holmes and more?

Yes, it does! Deezer even shows a few of the Die Drei ??? episodes as the most streamed albums and I was able to find Sherlock Holmes as well. I am currently listening to the Snowden story.

As an addendum to my post from two days ago, I must add the following:

• Deezer has an endless playlist called Flow, which contains your favorite tracks and similar music. With all the genres you listen to. I actually find it better than the mixes that Spotify always suggests to me.
• Deezer’s annual plan is actually cheaper than Spotify. In addition, there would even be a HiFi subscription, but I am not audiophile, so Premium is enough for me.
• So far, I’ve always appreciated Spotify for its curated playlists, but Deezer has many curated playlists as well.

What else I learned through online research: Deezer is available in almost all countries, while you can only use Spotify only in a few select countries. And some people think Deezer’s audio quality is better, because Spotify would probably add more bass to the songs. I’m not sure about the latter, though, if that’s just a rumor.

Spotify probably just did more intensive marketing and became the market leader as a result. Deezer actually existed a year before Spotify.

Anyway, I canceled my student subscription with Spotify (I’m not a student much longer anyway) and am now using the 3-month trial period of Deezer Premium.