I will have a car while in Tuscany for three days and will then be heading to Sorrento.

Is it better for me to drive the five hours or so down to Sorrento or take the rental car to Siena and hop on the train.

Originally, I thought the drive might be fun, but it doesn't look like there is a whole lot to see on the way and it may be more trouble than it's worth.

The trip is not scenic---mostly autostada driving---but easier than the train from Siena which may have 2 changes--it is not direct from Siena. I would drive.

It is not difficult but it is a loooong boring drive. This is just my opinion.

You will have a few train changes coming from Siena, including one in Naples where you will have to transfer to the local Circumvesuviana to get to Sorrento. I think I would drive, since you already have tge car.

I drove and returned the car in Sorrento after dropping my luggage at the hotel.