San Jose, California is 12 times larger than Jersey City, New Jersey.
Area: 38 km2 calculated
Jersey City is the seat of Hudson County, New Jersey. As of the 2010 United States Census, the population of Jersey City was 247,597, making it the second-most populous city in New Jersey, after Newark. Wikipedia
Area: 470 km2 calculated
San Jose is the third-largest city in California, the tenth-largest in the United States, and the county seat of Santa Clara County. San Jose is the largest city within Silicon Valley, which is a major component of the greater Bay Area. It is the largest city in Northern California. Wikipedia