The torpedo type work fine for me after adding weight. Others have not needed to do so. Weight can be added in a number of ways and is fairly simple.
One additional consideration - the torpedo keg buoys come with a short dip tube, while the ball and keg do not; they instruct you to cut an existing dip tube.
One additional consideration - the torpedo keg buoys come with a short dip tube, while the ball and keg do not; they instruct you to cut an existing dip tube.