what is more popular silver or black face plates

I prefere black, as silver is a visual distraction from the music being played.  

Definitely agree with @jwei's recall that it is cyclical. In the UK, I would say that at the moment 'premium' comes in silver; 20 years ago, it was black (and 20 years earlier, it was again silver).

Personally, don't care. I have a mixture, depending on what I find/is available/cheaper.

I agree with @max_sansui 

Black, out of sight, out of mind.  I just want to hear the music!  Cheers

I prefer black, but on occasion have bought used gear that is silver. At the moment, it's all black for me.

Has to be black... Black is pure class, doesn't stick out at night when I do most of my listening... Silver is a eyesore, and it looks cheap and unfinished IMO