From what I can see if the HGVC system, they have many great urban properties but many less beachside and international locations.
It depends on where you want to stay. The systems are different in location and focus. We added Vistana because it added complementary locations of Maui and Kauai to HGVC which is strong beachside on Oahu and BI. There are also other complementary locations.
Unlike Marriott, HGVC treats resale buyers well. They are aggressively adding new properties. Here is a list from the HGVC thread:
Recent Additions:
1. The Bay Forest Odawara, Japan (by Mt Fuji, 1 hour outside Tokyo), by Hilton Club
2. Borgo alle Vigne, Tuscany
3. The Residences NYC
4. The District, Washington DC, Georgetown
5. Ocean Oak, Hilton Head Island (beachside)
6. Ocean 22, Myrtle Beach (beachside)
7. Grand Islander, Waikiki (beachside)
8. Ocean Enclave, Myrtle Beach (beachside)
9. Hilton Villamoura, Portugal [added]
10. Hilton Craigendarroch Scotland [added]
Officially Announced
1. Saint Philip, Barbados: HGVC @ The Crane (beachside)
2. New York, New York: The Quin by Hilton Club
3. Cabo San Lucas, Mexico: HGVC @ Los Cabos (beachside)
4. Chicago, Illinois: Chicago Chicago by HGVC
5. Ocean Tower, BI (beachside)
6. Waikiki, bHC
7. Okinawa, Japan (beachside, new build)
8. Liberty Place, Charleston, SC, bHC
Rumored
- Turtle Bay, HI: HGVC @ Turtle Bay "rumored"
- Ambergris Caye, Belize: Mahogany Bay Resort & Beach Club @ HGVC "rumored"
- San Francisco, CA: "rumored"
- China: "rumored"
Even in locations where they overlap, each has it's strengths.
IMO I would like to see more European cities in both systems.