I guess it totally depends on your meaning of existence. Ask me if I'd rather lose three fingers on my left hand or both legs, the answer is easy for me. I play the bass. Without 3 fingers - well, what would be the point? But without legs - who needs to walk?
Ask Carl Lewis that same question - I doubt you'll get the same answer.

I'm sure that all musicians and music lovers would rather go blind, but people whose lives are not all about music, like Bill Clinton, Steven Speilberg and Britney Spears would probably prefer to go deaf.