Especially if you're not familiar with Boston, the idea of dropping off your car the night before (either at the airport or at an Avis office downtown) is an extremely good one. Lots and lots of road construction going on in downtown Boston and the airport, and the signs aren't always as helpful as people might expect them to be.

If you do elect the drop-off-the-night-before option, the Marriott Copley would be the best location: in the middle of restaurants, shopping, and lots going on. On Sunday morning, it's about a 12-15 minute taxi ride to the airport. A huge advantage of the Copley Marriott is that you can get to lots and lots of shops/restaurants in Copley Place and the Prudential Center without going outside: that can be a big advantage in late December.

My second choide would be the Long Wharf Marriott. It's near the Quincy Market area which has lots of restaurants, most of them undistinguished. However, anyplace you go is a 5-10 minute walk, and the wind howling off the harbor can make for a cold time (esp. for those who come from places where 38 F. is a cold day). The LW Marriott is about an 8-10 minute taxi ride to the airport.