Treasure Island is a 400-acre former military base built on a manmade island in San Francisco Bay. Plans have been in the works for years, and will result in "a mix of 8,000 low rise and high rise housing units and a denser core made of mid-rise buildings and skyscrapers..." according to The Architect's Newspaper.
Parkmerced, on the other hand,is a planned neighborhood of high-rise apartment towers and low-rise garden apartments in southwestern San Francisco, California. Lydia Lee reports that Parkmerced "will be updated with local retail, a MUNI stop, and a fine-grained network of streets and pedestrian pathways. It will also be made 4 times denser, replacing the low-rise apartments with new low and mid-rise buildings.