I looked at both of those hotels, but found the cash rates too high. If you aren't married to either Marriott or Hilton I highly recommend the Dress Code Hotel (and the breakfast is worth the $$ IMO) or the Mathis. I paid just over 327 Euros / night, which is a great rate central for Paris. The location of the Dress Code is, IMO, amazing. I will definitely stay there again. Do be mindful that it is not a full service hotel, so no concierge (though the front desk staff is very willing to help), no gym, small room and bathroom and small hotel (33 rooms), but for me it was perfect and for anyone that needs somewhere comfortable and clean to sleep, ideal. There is also a great supermarket right next door. I'd recommend room 306 or 406, but if you don't mind some occasional city noise they have rooms that face the front of the hotel. I booked the Dress Code using URs (fully refundable rate). You can very easily walk to le Printemps, Opera House, the Ritz, the PH Vendome, Galleries Lafayette, Monoprix and 2 metro stations.
I try to never book non-cancellable rates -- there are exceptions, but I purchase CFAR insurance when I do -- too many things can go happen / go wrong at this stage in my life.
Also, I highly recommend CityPharma if you like skin care. Do a quick search -- it has a cult following. Easy metro ride from Dress Code Hotel. I'd go early as it gets very crowded. Alain Ducasse's restaurant, Champagne, has an AMAZING cheese souffle, I tried to get a table at Le Souffle (which is a short walk from the Dress Code Hotel), but failed (only 22 tables, so book early if you want to secure a table for dinner).