To me, the key is having something to offset the location of the Cavalieri. If you are in Rome to see the sites, it is obviously better not to have to take a 20-30 minute ride to get to the city.
That being said, to me, the "something" is the Imperial Floor and Lounge. My wife and I have reservations at the Cavalieri for next summer. This is to be a special trip to replace the trip that we had planned for 2 years ago but had to cancel at the last minute due to a medical diagnosis that my wife received. Fortunately, the treatment has been successful and she shows no signs of recurrence. The reservations are on points. I have contact the Cavalieri and explained the situation hoping to get a "confirmed" NOR1 upgrade to the Imperial Floor (as a Diamond). All the Cavalieri would say is that IF there is room available, I would get it (In others words, no special treatment).
So I am basically at the position of taking the "risk" with the Cavalieri or using the backup reservation I have at the Excelsior (will be P at that time). My inclination is to cancel the Cavalieri and go with the Excelsior.