Grosseto makes no sense from San Quirico--Pisa may.

It takes takes a minimum of 3 hours to drive to La Spezia from San Quirico d'Orcia.

It takes a minimum of 2.5 hours to drive to Pisa from San Quirico d'Orcia.

So the only sensible choice is either to drive all the way to La Spezia, or drive to Grosseto and take the train. Driving to Pisa and then taking the train from there to Manarola doesn't make sense.

It takes about 1.15 minutes to drive to Grosseto from San Quirico d'Orcia (an easier town for locating the rental office) followed by a 2.5 hour train ride to Manarola.

Yes, one "loses" an hour driving to Grosseto, I would rather skip the extra hours of driving on the highways and negotiating La Spezia's city streets. There is a 9.45 train from Grosseto that means one can be in Manarola by 12.30 without a lot of stress and still be in time to sit down for 1.30 lunch.

Driving to La Spezia means spending 3 hours mostly on autostrade, and then having to deal with the city to drop off the car, and then deal with getting back to the train station and on to Manarola. By getting up early enough, once can still make it there in time for lunch, but not as relaxing.

Different courses for different horses. I'd rather do one hour of driving in the morning and be done with it than be looking for a car rental office after 3 hours of driving the autostrade, closing in on the lunch hour.

Ha--she took the bait!

The contrarian returns---with new names---after sitting out six months in the penalty box.

I have driven that route to Grosetto--it is a slow 2 lane road.

Which of your new names should we use?

>>>so if you stay in town, you'll have to work your way down the side of the mesa in the morning and back up in the evening.<<<

Not really. You can park on the far side of Orvieto and take the escalators from the parking lot or park below the train station and take the funicular.

Well, yes, I didn't go into the escalators/funicular. But that takes time also.

I love train travel and would suggest you take them as much as you can. That said, having a car to travel in the countryside and visit some of the smaller towns is probably a better way to go.
I'll be renting a car this Oct to do the same thing. I did find that the rental is much (30%) cheaper from FCO than from a smaller town.
Orvieto is a charming town and a perfect day trip from Rome.

FYI - Check the towns you're planning to visit and the dates you'll be there. Most museums are closed certain days or times. By the time I got to Orvieto, up the funicular, and walked to the Duomo - it was closed for 2 hours for lunch. I never got inside as I had a time crunch to get back to Rome and out to the airport to catch a flight.

>>>>I don't know why it costs more. I guess because it's more expensive to rent in Orvieto than from the airport. Renting from Orvieto was my original plan, then i scratched it when i checked with auto europe. <<<

I just priced a rental with Autoeurope (6 days) for FCO and one for Orvieto (same dates). The Orvieto pickup was cheaper (only a few dollars difference). I'm wondering what you may be selecting on Autoeurope to cause a difference. Typically airport pickups are more.

<<Typically airport pickups are more.>>

Yup, that's why I asked the question. Maybe the OP needs an automatic or something special that would be harder to come by in Orvieto.