Fonti di Pescaia has a quite good location for all who like walks, since it is located about 10-15 minutes from Il Campo. Hence, walking to the middle of town, you quickly are familiar with the ancient part of Siena. The only thing that I suggest to change is to organize a place for making a tea or coffee: I think that if there would be a possibility to prepare a tea or coffee in room, Fonti di Pescaia would be yet more attractive place.
Chez Liviana has a perfect location: close to Roma Termini and to the middle of Rome. This is the first advantage of that place. Second, breakfast is included in the price of room, and there is a small kitchen, when you can prepare a tea or a coffee. This is very nice, especially that one espresso for each day of your stay is free. There are two things that I would change: in rooms there is quite weak light, and I would slightly extend menu for breakfast (a small crossant may be not enough).
Dolphin Inn is located near London Paddington and it is its main advantage. Other factors are worse. For example, since in my room I had a very weak wi-fi signal, I had no access to internet in fact (going downstairs up to the basement as the hotel staff members suggested does not satisfy me). I think also that in each room should be something to sit down (e.g. a chair or a stool). Summarizing: hotel in a very good place with rather low ratio quality/price.
The main advantage of the B&B is a very good location; the main disadvantage is the noisy street what may cause problems for these people who want to go sleep early.
Light in my room was very weak