Barcelona, London, Florence, or Paris

Just curious on what people think of these options. For some context I am studying abroad next spring and am looking at these options. I have been to London and Paris before for a week and love both but probably Paris more. However my friend would be doing London with me whereas the other options would be solo. London also I would be housed in Lewisham 40 min outside center of city. Never been to barca or Florence but would also like a new experience and new place to see. What does everyone think?