I cannot speak for all of them. But, I can give my opinions on the places I have been to last year.
1. Vienna - Stayed at PH (opening week). Great location. Fancy room controls, bathtub, Would most definitely recommend it
2. Venice - First choice was Hilton Molino. Missed out inventory by 1 day. Stayed at Boscolo Venezia (marriott). Standard room was tiny. Not particularly near anything but hotel arranges a private tour of Murano and Burano.
3. Rome - First choice was Rome Cavlieri but stayed at IC Rome. Right next to the Spanish steps and a metro station. Room size is standard for Europe. The room and hotel could use an update. But, location is great.
4. Florence - Stayed at Hilton Florence Metropole. Room was OK. Liked the lounge area (high floor; combination of indoor and outdoor). Did not check out the pool area. Provides shuttle to some areas.
5. Lucerne - Stayed at the Radisson Blu. If you get the right room (like us), you could get a wall of glass with a great view of Mt. Titlis. Yesterday, I read that a botique hotel is being converted into an Autograph collection (marriott) and opens in July. You might want to check that too.
Good advice here, I will add:
2. Venice - stayed at Westin Europa, nice room, slight upgrade for SPG gold and a couple of cocktails on the canal. Hilton looked good, but a little further away.
3. Rome - Stayed at Rome Cavalieri, wouldn't really recommend it, back then it was super cheap (145K Axon) but the location is so far from the city that you need to take their shuttle or a cab to get in, IC is much better located.
5. Lucerne, yep, the Radisson was great.
Zurich, stayed at the Sheraton, it was fine, PH is nearby, and is the easy answer to a vendome approach.
Enjoyed Basel in Switzerland.
Previous trip to Switzerland took train to St Moritz, scenic car is epic, through the Alps.
When in Italy I enjoyed Milan for a day, PH has a great location near the Duomo, maybe worth stopping off on route from last location. If you are 'strong' I would say 1 day Milan 2-3 in Rome is enough. Our 4 days in Rome were more than enough, and we took side trips to nearby towns of Orvieto and perhaps another..
Trains are going to be a big value for you -Milan to Rome by train was really nice, Swiss trains are super, German I think are also..
might want to price out a Euro Rail pass.