All thte YC rooms have either first floor patios or balconies while only SOME of the BC rooms have balconies. You're right, though: the decor is the only difference between them, but it DOES give each hotel its own identity. The hardwood floors, nautical theme, and sober colors create a more formal air at the Yacht Club, while the pastels and surf-and-turf motifs make the BC more kid-friendly.
Which one you prefer is a matter of taste. I've stayed at both and prefer the YC - I like having a balcony all the time.