Would you rather be super-rich or super-smart if you would only be average in the other category?
wyld_dandelyon pointed out that even the low end of "rich" sounds pretty good. :)
But even if I took "average rich" to mean "average wealth for an American", I have to say that these are both catagories where being average is a pretty good deal. I wouldn't want to be destitute, or mentally disabled. But being just average at either is good. Much better than being an impoverished genius or a wealthy idiot.