WKORV is the original development, its about 10 years old now. WKORVN is about 5 years old. Although they are both Westin properties, they are treated as separate resorts with separate reception lobby/check-in and parking.
There is no physical separartion between the resorts and guests of either resort can use amenities of both resorts. The WKORVN has a full spa, salon. Guests of either resort can charge expenses at either resort to room. Exterior finishes of both resorts are identical.
Differences between the resorts is the view category. Buildings in WKORV are built directly facing the beach while the buildings in WKORVN are built at an angle. Units in the WKORVN tend to have better ocean views because of the angle of the buildings. On the other hand, there are no true ocean front units in WKORVN while the units at the end of the WKORV buildings are directly facing the beach. The units at the end of the WKORV buildings are much closer to the beach than the end units in WKORVN.
If you're looking to buy and oceanfront is not important, its probably a slightly better value in WKORV, but if pricing were the same and you were looking at an ocean view, consider WKORVN for the better views.