We are thinking of driving because the trains will take most of a day. Has anyone made this drive? Is it scenice or just a headache and better off with the trains? Obviously the trains are much less expensive so unless it is worth our time and money I don't want to do it. Please advise.

You're better off with the trains, unless you plan to do a lot of car trips in Tuscany.

I believe that the distance is over 330 miles from Venice to Siena. The trip by train can take as little as 5 hours (actually a little less). That's not bad. I don't think you will save much time. Especially when you look at price of car and the time to get to and at rental agency, etc. On the train, you could have a meal (additional time if you are driving). You can relax (as opposed to worrying about getting lost), enjoy the scenery or sleep, and you can visit with other travelers. I have met the most interesting people on European trains.

Cars are great when you have lots of time and want to explore, but if you are most interested in here-to-there, I'd take the train. I always feel the train is just part of the European experience.

If you need the car anyway, drive.
If not, train.

We drove last week from San Gimignano (which is near Siena) to Venice. Very easy drive, excellent roads. No problem at all. The distance between those 2 cities is 335 KM (NOT MILES!). Driving without stopping it should take you not more than 3.5-4 hours!

Thanks for the correction. I thought I was on an American site and looking at miles.