Our last booking was our first Mini suite aboard the Grand and we certainly enjoyed the extra room and couch. The bathtub gives one a much improved shower space. Plus the balcony layout extended further outwards rather than a narrow rectangle. This allowed seating for four persons.
But the decision as to price differential must be related to where you are going in March. A cool climate negates the better balcony but enhances the extra living space. This is of course reversed if your are to be in the tropics.