Reagan is the closest, but the flights into BWI are usually cheaper. There are plenty of shuttle buses to chose from, and depending on when you arrive, it would be about 20-30 mins to your hotel, or 1-2 hours on crowded shuttle in peak traffic. Driving in DC blows, and anyone not from there, but even from nearby east coast cities hate driving around DC. And, the last thing you want is to get lost in DC, the hood can change with a blink of an eye.