I've stayed at Grande Ocean, Barony Beach, and Harbour Club, but not Heritage Club.
Harbour Club is in Sea Pines Plantation, but not on the beach.
Grande Ocean is on the ocean, not in Sea Pines Plantation, but does have Sea Pines privledges.
Barony Beach is on the ocean quite a bit north. Some units are ocean front, some are considered oceanside, but may or may not have an ocean view. And some are garden view, a bit back from the ocean and kind of behind the adjacent Westin hotel.
All are very nice, and Grande Ocean is my favorite.
I think an exchange for a summer week might be difficult, in part because of the popularity of HH in the summer, and in part because of Marriott's internal trading priority (where other Marriott owners get first shot at any available exchanges.)