We visited the Guggenheim because the Neue doesn't allow children under twelve, nor infants without carriers and they don't carry carriers. Hmpf! We noticed upon entering the (G) museum that the hats worn by visitors were much larger, and of more interesting materials, than those on the street.
We enjoyed the "El Greco to Picasso" (favorites: Goya, Velazquez) exhibition (a compare and contrast design) as well as the architecture and feel of the building itself. It surely may be the fanciest yacht you'll ever board. (I was worried about the contractor's punch list as I saw myriad items that still needed "shoring up.")
David raved about the paintings of children section, and Molly, Annie and I preferred some of the non Spanish paintings when we stepped into the Thannhauser Collection wing for a minute.