Staying in San Gimignano vs. close to it w/ 2 teens

I presume you will have a car.
The decision is only yours, as you pointed out there a pluses and minuses with either choice.
Also, If you stay within the city walls, you may not be able to park your car inside and have to leave it outside the city walls at a parking lot. Car access inside the city walls, in the historic center, is restricted. Just one other point to consider in your conundrum.

I would think it's already late to get one of your first six choices, by now. So the decision may be made for you. Since "in SG" could be anything from a cramped apartment rental to a decaying mansion, it's hard to give advice.

Presumably you'll be daytripping in the car every day. I found the outside parking for SG to be very far (and steeply downhill) from the main part of the town. I think it comes down to whether you want an urban experience or a rural hotel experience. SG, while very attractive, is not exactly an undiscovered gem where you'll be rubbing shoulders with grandmothers in black dresses doing their hand washing in the village wash-pool! It's not a "small villages ... in the countryside." The places you saw in Band of Brothers are mostly gone.

We did not sleep in S.G., so I can't tell you what you really want to know: Will I have a "Rick Steves" experience after the daytrippers have all left for the day? But you need a ... I hate to say it .... place with infrastructure, like bars for standup breakfast, and laundromats and convenience stores.

I won't argue for our (not at all Agriturismo) luxury rural hotel outside Sinalunga. But it had a refreshing pool after a sweltering late July day of touring, and superb air conditioning, unavailable in many European cities, including Hiltons and Marriotts. Maybe June is cooler. But it was in mainly medieval stone buildings, with new electricity and plumbing. One reason the A/C worked so well is that the walls were two feet thick.

Tammy, just my IMHO but if you intend to do Florence, Lucca, Pisa and Siena. I'd want to stay in a decent transport hub (Florence). You do not mention if you're renting a car but it's easier not to drive one in some of these locations anyway. With just 4 nights/3.5 days and possibly 3 day trips, you don't have time for wandering about the countryside anyway.

BTW, Florence should not be combined with Lucca as a day trip, if that's what you mean by "Florence/Lucca". Florence is well worth a entire day or more in its own.

Yes we'll have a car, but will take trains if/when it makes sense.
Yes we'll do Florence on it's own and Lucca and Pisa maybe on the same day?
We went to Florence a decade ago and I remember it feeling too big city-ish, sandwiched in between Rome and Venice. That's why we were thinking about staying inside a smaller village, with some services, places to eat, stores.

Maybe SG isn't the right choice, based on what Time is saying? Can you suggest any others? Are there any small towns that would be a nice home base for hanging out in evenings once the crowds are gone?

San Gimignano is not the problem. San Gimignano is as good as any other town of similar size, but the reality is that if you stay inside the historical center of a town, you can’t drive your car to it. The car must stay outside the city walls, and that is true whether you choose SG (small), Siena (bigger), Monteriggioni (much smaller).

Personally, I would stay in Monteriggioni at this hotel:
http://www.hotelmonteriggioni.net/it/
It has parking, swimming pool, and it’s inside the city walls. Of course Monteriggioni is even smaller, but in my opinion more magic. You might actually get to know some local folks there.

Not a teen, but I was there for a day recently and knew it was small but looking down from the tower I could seen how small it is. Huge crush of crowds during the day and may well be magic at night but since I could walk the whole town in less than 20 minutes San. Gio would probably be the last place I would stay. Pistoia just outside of Florence is wonderful, Lucca is also wonderful lots of cultural.. Musical etc. events.

We are staying in Fiesole outside of Florence. We too will have a car and will tour around the Tuscany area but in the evenings and late afternoons spend it in Florence! It is fun to take the bus into Florence and leave behind the car since you are not allowed to bring the car into the center of Florence! Ciao!