i have stayed at the w a lot over the years. the upgrades are very hit or miss. depends on the occupancy rate and what rooms are clean at check in.
had some very nice rooms and a closet last time. never a suite. my feeling is the weekend is likely easier. check the rates for paid reservations that weekend and if they are close to the two sheratons i think you have a better chance. makes me miss the essex house where i got great upgrades. good luck