Aurora, illinois is 4 times larger than Elgin, Illinois.
Area: 412 km2 calculated
Aurora is a city in DuPage, Kane, Kendall, and Will counties in the U.S. state of Illinois. The second most populous city in the state, it is the 19th largest city in the Midwest and the 112th largest city in the country. Wikipedia
Area: 103 km2 calculated
Elgin is a city in Cook and Kane counties in the northern part of the U.S. state of Illinois. Located roughly 35 mi northwest of Chicago, it lies along the Fox River. As of 2013, the city had a total population of 110,145, making it the eighth-largest city in Illinois. Wikipedia