Check the difference in airfares, then decide
My family drives RT 70 frequently, Carroll County is farmland, congestion around the Frederick interchange is pretty limited
And again, Antietam makes an awesome side trip
Limited can vary. If driven on a weekday, the Maryland highways are packed with serious traffic. 70 out of DC goes from 7 lanes to the two lanes of US 15 in Fredrick. A natural choke point. So timing is important.