Day trip from Orvieto: Cortona? Arezzo? Other?

According to bahn.de, Cortona is less than an hour away, Arezzo is a little more than an hour. Trains are frequent during morning and late afternoon (I didn't check evening schedules), buses are probably less frequent. Both are beautiful hill towns.

I would also add Montepulciano. Take train to Chiusi Scalo, about 20 minutes, then bus to Montepulciano.

We were in Orvieto last week; we loved it! Do not miss Civita di Bagnoregio!! We drove to Bagnoregio in our rental car, parked, and walked across the amazing land bridge to Civita, but we read that you can do his trip by bus. We have been traveling in Italy for three weeks and I can honestly say that this enchanted village ranks at or near the top of our experiences. Plan to get there in the morning and have lunch! Unforgettable!

These would be my choice.

http://www.castiglionedellago.eu/eng/ easily reachable by train.

http://www.bestsmalltownsitaly.com/town/sorano-tuscany-center/ car only