Italy to Barcelona

Two very bad train options. It takes forever and a week by train no matter which route you take. You need to change multiple trains too since there isn't one train only that goes directly from either one all the way to Barcelona. You should fly. There are flights to Barcelona from either Florence and Venice and the flight is less than 2 HR long. Vueling Airlines is likely the best option. I'm pretty sure it's cheaper by air as well.

I would fly. Venice to Barcelona by train is 16+ hours. By plane is 1hour 55 minutes. Vueling is a budget carrier that flys this route. Make sure to read their luggage restrictions carefully. Even if you add the 30 minute bus to the airport and arriving at the gate an hour before it still beats a long train ride.

I would also vote for plane travel. We traveled from Barcelona to Rome last fall using Vueling and had great service - small seats - however a short flight. The Barcelona airport is excellent and there is an airport bus service that runs every 15 minutes from the main terminal to a couple of main stops in Barcelona.

I love European trains, but in this case I would fly. I agree with Joni that getting from the Barcelona airport to the city is very easy using the airport bus.

I also agree that a budget flight would be the best choice in this case. While the train trip may sound enjoyable, it will likely be long, tiring and boring (up to about 25 hours in length with as many as five changes - not my idea of an enjoyable holiday).

www.skyscanner.com can reveal other, competing airlines, as well. Tell your wife she can "see more" at your main destinations, instead.