i say go for the St. Riges... for a $375/night you gonna get there grand delux room (not the standard one.. which is also very nice ). the grand delux room is like a mini suite.. you gonna love it.. and i wont talk about the locatin.. otherwise i would go for the essex house.. usually they are very good in upgrading platinum to suites.. here is what i would do.. make reservations in both St. regis , Essex hous .. try to confirm a suite upgrade at the essex house the day before your arrival date .. if what you get is "oh, we are out of suites for your dates" then cancel it and hed to the wounderful St. Regis.. if you get a positive reply from the Essex house cancel the St. Regis reservation..

good luck