So 650M performs 91.6% better (41 versus 21 fps)? Where did you take your math exam
21 is about 41 divided by two. How can that ever be a 91% difference?
(41-21)/41 = 0,4878 = 48,78%......
The numbers were reported inconsistently: https://forums.macrumors.com/posts/17690462/