There are tons of (Singaporean, Taiwanese, Korean, and Japanese) expats in Park Island, rather than European and American expats. A number of Mainlanders as well. Perhaps this is the difference.
Park Island is on Ma Wan, which is more convenient for some -- close to the airport should you need to travel, regular ferry into Central, and ferries/buses into the western NT. It links to the Tsuen Wan, Tung Chung, and West Rail lines along with many bus options. However the island itself is perhaps not as much of a self-sufficient community as DB, and unless you like Japanese food, Cantonese food, or Cantonese-style Western diner food, then there are not many options. (The grocery is, however, much better these days.) Perhaps it is also not as English-friendly -- I speak Mandarin and enough Mandarin-influenced Cantonese to get by easily, but some English-only friends mentioned some linguistic barriers. (My English and French-speaking mother, however, had no problem making herself understood on Ma Wan or anywhere else in Hong Kong, so perhaps this is not the case for everyone.) Additionally there is now the awful, awful Noah's Ark (and thus many more tourists). (This is the reason that we left Ma Wan.)
We did not live in the Park Island complex when we were there, choosing instead the village houses (which were larger and, with a rooftop, over double in size for the same price); however we had/have many friends in the complex. The club house facilities are all decent.