Rent a car or bus?

If you rent a car in Spain and drop it in Italy, it will have a very large drop fee. They can't rent a car in Italy that has Spanish license plates, so it will have to be transported back to Spain. Guess who pays for that.

I say rent a car once you get to France and drop it before you cross into Italy. In Spain and Italy you can use trains and buses.

You'll see as much as you can... how much time do you have? When's the trip?

I will be there for a total of 12 days. Thanks for the tip about renting a car only in France . Might be a great option .

There's generally good train service along the coast. I don't mean the tracks run right along the Mediterranean with sea views everywhere (though they often do), but the train connects most of the coastal cities and towns. A car can be very helpful when you want to travel inland in an area like Provence. Some of the most charming hill towns have little if any bus service (and trains don't go up to hill towns). Whether it's useful to have a car for the entire time you're in France depends on what places you want to go, so you need to get hold of a good guide book to southern France and dig in.

Understand that you could easily spend more than half your entire trip just seeing Barcelona (nine days in the city was definitely not enough for me), and there's easily over six weeks' of stuff to see along and near France's Mediterranean coast. You're going to have to be painfully selective.

I'd suggest thinking about this from a practical standpoint: If you're going to leave places that you're really interested in unvisited (and you certainly are), which ones are easiest to return to? (That would be places like Barcelona and Nice with major airports.) If you decide to rent a car, I'd recommend tilting in favor of visiting places you'd have a hard time reaching if you had to depend on buses and trains--places like Provencal hill towns. The car will be of no use to you in larger places like Marseille and Nice, and large cities will suck up a great deal of your time once you set foot in them, as compared to being able to visit multiple small towns in a single day). The car will be a major parking burden even in the small coastal towns, where simply taking a train will be better.