SIM card in Italy

TIM has good plans

Thanks for the info.

Tim and Vodafone have similar plans and prices.
Wind is a bit cheaper.
This is from my cousin's daughter (who has Wind). His father (my first cousin) disagrees, he has TIM. But he's a manager with Telecom Italia (TIM parent company) therefore his opinion is probably biased. I've been a Vodafone customer since the time cell phones where first sold and I have no complaints.
I know nothing about 3 (3 is the name of another large provider)
In your shoes I would go with any of the above. It won't make a difference considering how long you will be there.

I very much confirm what Roberto said: I have Vodafone since my first cell phone and I do not have many complaints. I also have Wind on my latest smartphone, it is a bit cheaper but coverage is a bit more erratic. Most people have TIM and go along with it.

Thanks to everyone for all the advice.