Volterra or Siena?

If you haven't seen a roman theater (other than in Rome), go to Volterra. If you have, go to Volterra anyway. Siena is overdone, full of tourists, and bores you to tears after a couple of hours. Volterra can keep you occupied for a good day and a half.

I visited them both on the same day in 2008. My impression was that Volterra is a quiet hill town with an impressive roman amphitheater and alabaster carving studios. Siena is a small city, more bustle and (subjectively speaking) a little more cosmopolitanism and style. I could be totally off historically, but Volterra felt and looked more Medieval while Siena felt and looked more Renaissance. My choice would be Siena, (there's certainly more to explore there) but you can't go wrong with either, they are both quite beautiful in their own ways. Enjoy!

Stay in Siena, day trip to Volterra.

Siena. Volterra is too small for 2 nights, you will see everything in a couple of hours. Unless you have a car, and can drive to San Gimignano, or other small hill top town, base in Siena. You will enjoy the small streets there, the impressive Duomo. Take time, if you are physically able to climb to the top of the bell tower for fantastic 360º views of the surrounding hills, and down to the piazza.

Siena offers many more places to eat as well, you can sit in the piazza at a cafe to watch the locals and tourists pass by. Or get a gelato and stroll around the shops.

Ive stayed in Voltarra arriving late PM and leaving the next morning.It is a nice town but small.Siena would be better for 2 nights.Day trip somewhere the second day.

I stayed 2 nights in Volterra (Albergo Etruria) and had no problem filling my time with interesting activities. It's much smaller than Siena, which is part of its charm. That said, Volterra is more difficult to reach by public transportation than Siena, which may be a consideration. You cannot go wrong with either choice - both are great.