You know, any tour anyplace is a matter of picking and choosing what you want to see and how much time you can budget.
Pisa has one big attraction -- the Leaning Tower. As pointed out above, there are many other things there that are interesting, the Baptistry being a main one. But there are many many churches in Italy equally interesting. So most people budget 20 minutes here for "the picture" and then move on.
Florence, OTOH, is a place of many amazing things to see and do. It is totally impossible to see it in depth in a few hours. But when we cruise, that is the choice we make. The cathedral and the famous doors are the centerplace, David is a must, and then just a bit of time for all the rest of the city and the museum.
If you are going to try it all in one day, quick efficient transportation is the main thing. Frankly, I would not try to navigate local transportation on my own when I am in a hurry. Missing a connection anyplace messes up the whole plan.
The ship's excursions are usually highly efficient and move from one attraction to another on schedule. Of course, that means THEIR schedule. We have found, in Italy as in many other places, that hiring a private guide gives huge advantages, and allows us to see what WE want to see in accordance with our priorities. I strongly suggest finding a guide who will work with you and plan it YOUR way.
We used Dock and Discover Dock & Discover Tour Operator Civitavecchia Italy Escursions to Rome Florence Pisa Venice Pompei – Private shore excursions
iin Tuscany and were very happy with the way that they worked with us.
Have a GREAT cruise!