I think it depends on how a person drives, specifically how fast you're going on the highway and how much you're accelerating in the city.
If by "highway" driving a person means urban highways at average speeds under 70, then you'll get great mileage. If by "city" driving a person means quickly rushing from stoplight to stoplight, then yes your mileage will suffer in the city.
The lower EPA highway rating is realistic on rural interstates at 75-80
MPH. The higher EPA city rating is realistic if you are driving at speeds from 20-45
MPH with a lot of sudden acceleration.