I favor solarized light but it’s not available in the UI. The default light is a bit too bright for me though I will put it on sometimes when I get tired of feeling like I’m in a cave. Explaining my votes.
I prefer One Dark because of its perfect mix of contrast and colors.
Other themes I tried are usually focused to one color or tint much stuff with one color and have their background tinted too much, which is something I personally dislike.
Finally, the last reason for me to like one dark is, I like blue.