Ferrara or Bologna

I would say spend the nights in Bologna and travel to Ferrara. It's only about a half hour drive on A13 to get to it. Haven't been there yet but there is supposed to be a pretty good archeological museum in Ferrara.

Earlier this year we stayed in Bologna and did a day trip to Ferrara and would do it that way again. The only thing is that Bologna hosts many business conventions/trade fairs and at that time accom becomes scarce and more expensive. If that is the case when you want to stay you may find the decision made for you!

Ferrara was easy to get to by train from Bologna, about 10 mins walk from the station to the small city centre, I believe there is also a bus. The Tourist Info lady at the station was very helpful.
We had a relaxed day mixing sightseeing (the Este Castle and the Cathedral) with wandering around and lunch. Lunch was at a wine bar where Copernicus lodged in 1503 when a student at the University! Bicycles are the mode of transport in the narrow city centre streets. There was also a lively open air market going on, it was a Friday.

But don't neglect Bologna itself, enough to keep you occupied for at least two days or more. We really liked the place.

Whatever you do, don't go to Ferrara on a Monday! I did it last minute without any planning and it was a mistake. Not much to do or see and most of the decent-looking restaurants were closed. Otherwise I would definitely stay in Bologna. Or maybe Parma.

We recently returned from Italy. We had driven by Bologna on the autostrada a number of times and finally decided to check it out so we spent 1 day and night in Bologna. It is a lovely town and we enjoyed our stay here immensely. The helpful TI in Piazza Maggiore has a brochure for 1/2 day of sightseeing in Bologna. Have never been to Ferrara so can't help there.

Loved Bologna. It's a college and convention town but not terribly touristy. The food was great and shopping was very good as it was of high quality and not of the "tacky tourist" variety. There are a lot of places to eat and shop along the streets that radiate out from the Piazza Maggiore, especially to the left of the Cathedral facade.

Both towns were delightful. In Ferrara, I'd highly recommend you check out the frescos in Palazzo Schifanoia.
http://en.wikipedia.org/wiki/Palazzo_Schifanoia

In Bologna, I recommend you eat without stopping!