spottydog is probably right (as usual
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)
You are correct that Es Cana is a "nice" resort - very family orientated in term of entertainment etc.
Santa Eulalia is very good for perhaps a more "mature" holidaymaker in terms of entertainment, but does boast some of the best eating places on the Island.
Still some very good Hotels at each resort - for the Clubs, transport is not usually a problem, you can get to most places on the Island (for Clubbing) from Santa E in about max 30/40 minutes - depending on the time of season of course.