There are 3 most popular markets that gives back revenue the most (compared to other) - Spotify, iTunes, and Google Music (Google Play), but Spotify seems to be where you get the most traffic and it actually makes sense because how well implemented it feels. It’s really great for discovering new music. Bandcamp is also good but there you need to deal with tags as the main search function and plenty of stuff gets mis-tagged compared to what the actual content is. It’s also so bloated with half-assed efforts because everyone is a producer these days and in BC it’s free-to-upload just anything.
Now with Spotify, once you get on their database successfully it starts generating stuff around your artist profile and the most important thing is an appearance of “similar artists” tab. I don’t know how they define similar music to yours, but It Just Works™. So once you’re there you basically become connected and people can find your music while just casually listening their Spotify auto-generated music playlists that include there similar artists they dig which appear in that tab. And these playlists are crazy good and even being generated by genre. You just keep going, keep listening non-stop, it’s just wonderful to hear new stuff just like that rather than clicking bunch of links on BC and hoping it’s something good but it’s actually Kid Rock’s Christmas album in reverse.
Now entire revenue thing is pretty small but it’s better than nothing. For me, Bandcamp pretty much pays for DK services so my advice is to treat BC as an official artist page/the main hub. Spotify & the rest of gang should be the final step of final-final product you’re proud of. No random “ideas” and unfinished i’m-too-lazy efforts, that’s what Soundcloud is for (I would consider it the lowest-tier) so at least leave a good first impression. Finally, it’s all about accessibility and that’s the reason why streaming services are so successful. It feels more quality-controlled too because you have to pay to get your stuff there. Times have changed so adapt and don’t be like Tool guys who don’t have their albums out there because they’re so old-school-cool. A good thing that they’ve been famous before that so there’s still plenty of dad-rockers still buying their CDs. It’s all about getting your stuff out more in public rather than cashing in. I would say it’s a decent investment that just takes off really slowly.