Day trip from Venice?

Padova is closer, so less time and money involved. For walking around and seeing the sites, its great. There is a single street car from the train station to the center of town. Many things to do. Scrovegni Chapel with its Giotto Frescos is top of the list, but you do need a reservation. Great open air markets at the Piazza dell'Erbe, University with its Anatomy Theater, Basilica of St Anthony, and more.
I haven't been to Vicenza, hear it is also a nice town. Verona has a long list of sites, starting with the Roman Amphitheater. Take your pick.

Second vote for Padua!

Padua (Padova) is an easy 26 minute train ride from Venice.

Besides visiting the Scrovegni Chapel, you might want to visit St. Anthony's Basilica ( free).

There is also an open air market on Saturday mornings at Prato della Valle and the best gelato is 'Pretto' gelato found in Padua & Verona.

Get the Rick Steves Venice/Veneto book. It has info on all those options. I would suggest Padova OR Verona for the day. Not both.

I agree with Michael; don't squeeze both towns into one day trip. Pick one and devote the whole day to it. Any of the above are great daytrips from Venice. Vicenza is full of Palladian architecture, whereas Verona and Padova have more variety in terms of sightseeing. Vicenza has more of a small-town feel compared to Verona and Padova, IMHO. If you want to see the Scrovegni chapel in Padova, be sure to reserve well in advance. I actually prefer Vicenza and Verona to Padova, but I am partial to smaller towns which are easy to navigate on foot. However, Padova is well worth a visit, if only to see the Scrovegni chapel.

Wow, thank you all for your helpful advice. I am new to this forum, you guys are great! We will decide between Verona and Padova and spend the day there.

I like Vicenza, but I'm amazed by Palladin Architecture. To see this town lit in the evening is truly beautiful.
I think you could see Vicenza and Padova in the same day. They're only 25 min from each other.

Padova. Padova. Padova.
Easy, quick, 25 minute train from Venice. Easy, flat walk from Padova train statuon to tourist sites (Scrov. Chapel, St Anthony's Basilica, Excellent mini tour of historic Univ of Padova). All within easy 10-15 minute walk from train station, through beautiful old-city architecture. Ahhhh....one of my favorite places in all of Italy. Do read R. Steve's suggestions, spot on.

Enjoy!

Much as I liked Padova, Verona would be my choice. Besides the Roman Arena, there are lots of other sights. Google "Verona Card" to see what they are.

I haven't been to Vicenza.

It's a difficult choice, but in the end, I would go with Padova.

If you decide on Verona, it will be easy-peasy to get an early morning start, check out the market in the morning in Vicenza and spend the afternoon and have dinner in Verona before returning to Venice. The train trips will not take that long. TC