It would be very nice to be able to choose between the default song quality when you are on data and on Wi-Fi, so at the end you would choose between three different music qualities instead of the actual two (streaming and download)
Hi. That's why there is the automatic quality option. Spotify may not explain this very clearly but what it is supposed to do is the following: when you are on your data plan it will set itself on normal quality which is the best way to save data plan, when you change to wifi it will set on the best quality possible which it would be mostly the extreme quality depending on your internet speed.
My settings on my phone are: streaming-> automatic (saving data plan) and download->Extreme quality (I'll always download on wifi)