Pasig is 74% larger than Pasay.
Area: 18 km2 calculated
Pasay, officially the City of Pasay, is one of the cities and municipalities that make up Metro Manila in the Philippines. It is bordered on the north by the country's capital, the City of Manila, to the northeast by Makati City, to the east by Taguig City, and Parañaque City to the south. Wikipedia
Area: 31 km2 calculated
Pasig, officially the City of Pasig is one of the highly urbanized cities of Metro Manila in the Philippines and was the former capital of the province of Rizal prior to the formation the National Capital Region. Wikipedia