SubRed all the way. The font on Smart Dark makes my head hurt.
Since I didn't discover until ten minutes ago how to change the style, I haven't had much of an opinion before now. And, predictably, I prefer the one I'm used to, smartDark. Brightness tends to hurt my eyes, and I'd much rather read a night-looking board than a day-looking one, if that makes sense. Especially if I'm doing my browsing with the lights off.