Florence: the two Starwood properties are lovely but if by central you mean the Santa Maria del Fiore/Uffizi/Piazza della Signoria area, then they are not centrally located
The Starwood properties are located in the centro storico of Florence. They are a few minutes on foot (maybe 10?) from Piazza and they are far, far more convenient to sites than the Holiday Inn - which requires a 20 minute bus ride to get to the same area.
Ultimately the issue of 'central' location is relative. There is a strong argument to be made, for example, to avoid staying close to Piazza San Marco in Venice - precisely b/c of the crowds, tourist trap restaurants, etc... associated with that area.