If you're asking about the 2 stateroom categories, the main difference is the size of the bathroom/shower. The living room area and sleeping arrangements (sleeps 3 or sleeps 4) are the same.
There are similar categories that have a larger balcony (B6, M6) and the aft-facing staterooms have different characteristics, different balcony sizes, etc. but for side balcony staterooms, the balcony and Club balcony are mostly the same.