I prefer no syntax highlighting because I wear glasses, and the resulting chromatic aberration makes it difficult to read.
[1] (How strong? Well, the current frames I'm wearing aren't the frames I initially chose; they're the frames I chose out of the set of frames that have the earpieces connected far enough back to allow them to fold closed given the thickness of the lenses I wear. The fact nobody warned me about this when I picked out my first set of frames indicates it likely doesn't happen a whole lot.)