IMO Ashkenazi Jews are on average smarter.
I have met a few Ashkenazi Jews that were not smart in the least, so it is not always true.
Nobody, in this day and age, could write, with computers, staff, and preeminent scholars in collaberation over 20 years, what Moshe ben Maimon did in ten years, the multivolume Mishne Torah, which he composed on the run and in hiding and from memory. I think any Ashkenazi’s IQ would be hard put to match that.