From that page:
According to George Pólya:
“The only student of mine I was ever intimidated by. He was so quick. There was a seminar for advanced students in Zürich that I was teaching and von Neumann was in the class. I came to a certain theorem, and I said it is not proved and it may be difficult. Von Neumann didn't say anything but after five minutes he raised his hand. When I called on him he went to the blackboard and proceeded to write down the proof. After that I was afraid of von Neumann”.
https://www.quora.com/What-was-John-von-Neumanns-IQ-Was-he-s...
The conclusion seems to be that he had a higher raw IQ but Einstein was a 'deeper' thinker and better aesthetician. General relativity (which took Einstein 10 years of 'thought experiments') is often considered the greatest achievement of any single human mind. In Einstein's words:
"After a certain high level of technical skill is achieved, science and art tend to coalesce in aesthetics, plasticity, and form. The greatest scientists are artists as well." - Albert Einstein, 1923