I plan on spending a week in Tuscany visiting several hill towns, Trying to decide on the best place to base myself for day trips. Thinking about either Siena or San Gimignano, or possibly an agriturismo in the general area. Any thoughts?
Mike, how are you intending on getting around? That can make a difference.
I will have a rental car.
An agriturismo might be nice, but any sort of nighttime activity will be in the towns. What about Arezzo, Pienza, Montepulciano? or nearby?
Siena is great and a different city after the tour buses and daytrippers leave.
Castellina in Chianti, Greve in Chianti and Montalciano all make good bases for Tuscany.
Booking.com shows a lot of agriturismos and farm stays.
Use the filter for editing.
Use Rome2rio.com for estimates on travel times between places on your list.
If you've never driven in Italy be sure to learn about ZTLs.
Here are some different ideas.
Montecatini - on the Florence/Lucca train line and easy day trips to those cities. Also, a small town, typical Italian, and do visit Montecatini Alto, a cute hilltop above the city.
Orvieto Umbria, but close to roads and easy to get to Tuscany.
Montefalco, also Umbria but close to Assisi, Perugia and even Siena.
Siena is good for sure.
Panzano on the east side of the A1 and in the heart of wine country.
I would definitely recommend staying in a town rather than out on a farm (agriturismo). Your towns could be anyone of more than a dozen good choices all of which work logistically to do what you want, I am not sure there is one answer.
We stayed in Pienza and loved it but think would have been just as happy with other towns as our choice.
Would love to stay in Siena but of all of the towns I am thinking of could be the most challenging to get from your car's parking lot to your lodging each day so may be the one time staying a little outside of the town's center walled area works better for your purpose. The smaller towns it is easy to stay in the center of town and yet be not far from your parked car.
The benefit of the Agriturismo is you would have easiest access to your car at all times. Downside is you have to drive to everything, no walking around and enjoying the atmosphere right outside your doorstep a town provides not to mention dining/drinking options.
I found Montecatini to be a brilliant and easy base to move around via rental car and train.