We will be renting a car as we leave Florence and go to explore Tuscany and Umbria. Our last overnight is in Viterbo- mostly for the area around the town and because of connections there. From Viterbo we go to Rome. Should we drop the car off in Viterbo and take the train into Rome or drop the car in Rome at either the airport or the train termini? Thanks
Totally up to you.
I would also take into consideration how much luggage you will have in the trunk at the end of your journey. If a lot, I wouldn't want to deal with loading it and unloading it on a train. In that case it will be much easier to drop your car in Rome at any convenient city location, and transfer to a taxi from there to your Rome hotel.
If you manage to keep only one piece of luggage that is easy to take aboard the train, then you can drop the car off in Viterbo. Europcar has an office walking distance from the train station in Viterbo.
You could also decide once you are there. There is no penalty in Italy for changing your mind at the last minute. I do that all the time (I nearly always use Europcar). Just did that in Florence last month. Had booked initially my return at the Florence airport, instead, just an hour before the rental period was up, I changed my mind and drop it off at another office at no extra charge.