If the fall is sufficiently long, they reach different terminal velocities, which are proportional to the square root of their masses.
What does sufficiently long mean in practice?
It depends on the drag coefficient and forward projected surface area of the bottle. My mildly informed guess is that it would take between 20 and 30 seconds.
EDIT:
Actually, I've just tried dropping 1.5 litre bottles from an height of about 1.8 m. Even if the fall lasts perhaps one second, the empty bottle starts to tumble much more than the full one, and hits the ground a noticeably later.
Another month has passed and here is a new rationality quotes thread. The usual rules are: