There is nothing to settle - it is all about personal preference. You would also need to define what "best results" even means. Measuring dev productivity is a notoriously bad idea, so I just go with "That which makes me enjoy the work the most."
That being said, I waffle between 90s singer/songwriter music, 80s alternative rock, and a constant soundtrack of Joan Armatrading.
When I’m trying to create new stuff, it has to be no-voice. Multiple genres are ok, but words are distracting. Quiet always works, too. For wtf debugging, anything with a hard edge is good. (Voice or not). I’m either idling awaiting inspiration or chasing an idea. If the latter is deep enough, the music sorta goes away.
For me it's instrumental. Language distracts me. I also do well with something that has a groove. Some type of funk seems to work really well. YouTube has all kinds of instrumental funk music that works well.
Check out: musicforprogramming.net
I believe every study has shown music of any kind results in a 0x to 0.5x productivity hit.
electronic
Depending on my mood, anything from death metal to elevator-music jazz. I usually settle on some kind of house/trance with a pulsing beat, though. That's mostly when I know roughly what I'm writing, and I'm just getting the code in place.
And then, after working like that for a couple hours, my brain flips and I need as close to perfect silence as I can get, so I pause the music.