You said last 12 months. I counted from november 12 to march 13, before his injury spell. That's 5 months for Messi. During the voting for the uefa best player award, in august, cr was the 3rd with only 3 votes(messi had 14, ribery 36). So the claim cr was the best for the past 12 months isn't real. Cr also started this season slowly, he started shining the past 2 months. But somehow it seems it was the whole year for some.
I simply think that over the last 12 months Ronaldo has outperformed Messi