If you could only stop at one of these two towns, which would you select and where would you eat? Thanks!
I have only been to San Gimignano and really liked it. Next time I hope to visit Volterra. If I could only choose one? I don't know. San Gimignano has a great medieval feel and everything is built from stone. The towers make it pretty unique. It's definitely touristy but I didn't think prices were any higher than other towns we visited.
I can't give restaurant recommendations. We tend to eat based on looking around or recommendations from locals. We had three kids in tow and they survived on only pizza and gelato. My wife and I usually picked up snacks where the kids ordered pizza. In the evenings we wandered alone until we found a nice place frequented by locals.
I have been to both towns and found Volterra more interesting. Parking was easy and free and although very hilly, Volterra is very walkable. We had lunch at a RS restaurant where you select your food from a glass case--sort of cafeteria style--it was very good and had great atmosphere. In the evening this place becomes a regular restaurant. We had lunch at a pizza place in SG. I have to say that SG is easier to get to from many Tuscan towns whereas Volterra is a bit out of the way.