I have stayed at the Shelburne several times and two of the others hotels in the 'Manhattan Suites East' collection. It is almost like staying in a small NYC apartment. The rooms are very clean, the staff is great and they have a wonderful gym. They also have a restaurant, but I haven't gone yet. I have stayed in a studio and a one bedroom (small kitchen, living room and bedroom.) It is also located in a great neighborhood. Close walking distance to Grand Central Station for the Subway. Staying at the Shelburne will not disappoint you, especially if you are out and about enjoying NYC.
However, PAMOKW is absolutely right -- The Plaza is THE PLAZA, and that is a different NYC experience. Have fun in New York!