Perhaps we should also be looking at population density:
Stockholm: 11,802/sqm
Oslo: 4,268/sqm
Helsinki: 3,670/sqm
Stockholm: 11,802/sqm
Oslo: 4,268/sqm
Helsinki: 3,670/sqm
Wikipedia:
Helsinki: 3,070.08/km2 (7,951.5/sq mi)
No matter how you slice the figures, Stockholm seems to be a bigger denser city than Helsinki or Oslo.