The question is stupid.
Butt ugly people who are intelligent, want to be pretty.
It depends on the extremes- if you were really intelligent then you would relise that being intelligent is obviously better then having good looks. You would probably be never happy in your life though, as it would make people reaching out to you rare and your chances of having love almost nil.
If you were stunning and dumb as a post, you probably wouldnt even pay thought to this matter.
I would rather be average in both then on extreme in either.