If you choose Tossa del Mar as your destination, Hotel Diana is the best choice in town - beautiful architecture, nice service, and great location. It may only have two stars but it is a delightful and hospitable small hotel. The hotel is centrally located with an excellent view of the crescent shaped beach and the castle on the southern side. We had the good fortune of staying there during a 3-day beach football tournament and had a superb view of the action from our balcony. I agree with the reader that a balcony room is important. It really defined our stay. Try to get one on the 2nd or 3rd floor. The hotel room and bathroom are fine but not exceptional but we spent a lot of time on the balcony. The breakfast buffet on the terrace is very enjoyable and the hotel has a nice bar on both the street level and the balcony above. I recommend their mojito.
The hotel was very helpful to us during our stay. They arranged for a taxi to pick us up in Barcelona and for the return trip as well. Be sure to ask about the taxi accepting credit cards. They arranged for that on our trip to Tossa but our driver for the return did not accept a credit card payment.
Now, some travelers may debate whether Tossa is the perfect Costa Brava experience. We liked Tossa a lot but it's definitely a beach town and I would define it as a family beach town. Kids will have fun there. So, if you like to go to the beach, Tossa is great. It's not too big like the neighboring Lloret de Mar to the south. However, some of my Barcelona friends like to go a little further north and enjoy a little more seclusion. My wife and I spent 3 nights in Tossa and enjoyed it. There are plenty of restaurants in town and you generally don't need reservations.I recommend Tapas del Mar as the best and you will need a reservation there.