I would say blanks, but im sure im in the minority. Once you can touch type, the only reason for legends is aesthetics. Personally, I havent yet used blanks, but I have a few sets of blanks coming in the mail that im super excited to try out.
Ultimately though, my goal is to get some white blanks have some custom artwork sprayed on them. I know several artists that work in similar styles as to what im after, the trouble is choosing the best one without the others finding out I didnt pick them.
I only mention this because I dont necessarily think the options should be just blank or legends, rather they should be legends or no legends. That way you have a bit more option in the aesthetics of your board. Think of blanks as a canvas. Some people think legends are beautiful artwork, others thing they are garish.