I have stayed at both hotels numerous times. Commander is an older hotel on the Green in Cambridge. Elevator is a challenge, but the hotel is well kept and very nice, if you are willing to accept the nuances of an updated older property. The Sheraton is very nice. Both hotels have treated me well as a platinum, with nice upgrades on most stays and an occasional SUPER upgrade (got a suite that must have been 1500 sf in the Sh. Boston once - wow!). The clerks at the Commander have noted they prioritize among platinums, but they said it was based on frequency/stay pattern at that hotel, not price. Altogether, two excellent hotels with good treatment of platinums, but much different in their personalities.