Car will be faster, but I recommend T, unless your flight ends up delayed. 11:05 is plenty of time to catch the subway back and the tolls to get to the airport are fucking ridiculous (Like $7 each way now, I think). Even if you'[re delayed by like half an hour, if we can get to South Station via the silver line before the T shuts down, taking a cab back to my place would still probably cost less than actually driving there.
Unless you've got like eight billion bags, that is. If you'[re traveling with anything less than three or four bags (Easily carried between the three of us), we'll be fine on public transit.