With the perfect brain one could create a workout schedule to create the perfect body, Therefore attaining both.
U NEED A BRAIN TO WORK TO A PERFECT BODY!
With a perfect brain (assuming this means you contain all knowledge) you could also create yourself a perfect body with it.
I agree with the other comments
a perfect brain helps build a perfect body.
I think that these options are just unfair. Trying to choose between a perfect body and a perfect brain is like choosing bewteen being a cute dog or being Steven Hawking. Its absurd that anyone would rather be a dumb hottie and do nothing with your life. People who have a good mind at best would know that it doesn't matter how you look it matters how you act.