Earlier quoted context omitted.
How does it compare with the Metropolitan Museum of Art in New York?
It's a great museum, among the best museums (full stop) in the country, but it's less than 1/4 of the size of the Met.
If you are interested in specific individual collections then size might matter; if you are interested in Polynesian art, then possibly you could exhaust the Met's or Chicago's collections (I don't know).
But in some respects the two museums are the same size. And to go off on a tangent, I now find that I gain much more by spending a long time, maybe 30 minutes each, with a few works of art, rather than spending a few minutes each with 100 works. So for me, a museum with 10 great (IMHO) works would be plenty big, and better than a museum with 100,000 works that I have to sort through or walk past to find the ones I'm interested in. (Though the odds that the 10-piece museum would have what I want are a bit longer.)