I used to live within a mile of GAI. It's really a wash road-wise on weekends, nights, or off-rush-hour. I'd probably give the nod to FDK if the planned time is anything but morning rush hour.
Assuming non-rush hour traffic, it's a quick hop on the interstate from FDK, and very few traffic lights once you get off. From GAI, you've got a ton of traffic lights.
GAI's under the Class B and inside the SFRA. Those are generally non-issues, but they do add time & compress the traffic a bit lower in altitude. Add in the additional time in the air, and KFDK probably is faster in terms of total time (for non-rush-hour).
That said, either one works.