I would highly recommend staying at Claudio's apartment.
Communication was excellent and Claudio was kind enough to provide us with some useful tips for things to do in the city. Claudio took the time to meet with us and explain everything about the apartment and during our stay kept in contact to make sure that everything was to our satisfaction.
The apartment is perfect for 2 but would probably be a bit of a squeeze for any more. The second bedroom may be better used as a lounge as without it there isn't anywhere to sit and relax, however, with all the time we spent out exploring Rome this was not a problem.
Thanks again Claudio.