Which of these 2 sentences is more visible to you?

Which of the following is more readable to you? A or B? The smaller text on one of them fails WCAG 2.0 accessibility guidelines for both AA and AAA. Whereas the other one passes AA.

A

B

I think you'll be surprised to see which one passes. I tweeted the the accessibility test results here. We all rely on these accessibility guidelines to build usable websites and this, in my opinion, is doing a lot of harm to readability.