I haven't heard anything about people arguing about the size of the cabins in the Epic, but I received an email today from NCL. It states that the Deluxe Family and Deluxe Balcony Staterooms (Categories D1-D5) are 245 sq.ft. including the 56 sq.ft. balcony. Family balcony and balcony staterooms (Categories BA-BK and B1-B3) are 216 sq. ft. including the 65 sq. ft. balcony.
Anyway, this is straight from NCL's VP of passenger services.