MAC would be the most consistent thing and easiest to measure, so I'm sure the fingerprinting is based on MAC address. It's not hard to change your MAC address on Windows with Intel adapters. Maybe not as easy as clearing cookies, but not crazy hard either.

Marriott should provide an option to deregister devices. Some people sell their devices or have them lost/stolen, and I'm not crazy that if these things happened to me, that someone could perform Internet activity at a Marriott on a device/connection that would be tied to my name.

(Marriott should also push their hotels to start switching to Hotspot 2.0/Passpoint so the logins are automatic as part of the connection process & all connections to access point are individually WPA2 Enterprise encrypted instead of being in the clear, but progress takes time...)