most aftermarket lightweight flywheels are both lighter (obviously) and more hardy (able to take abuse even better) than the stock flywheel.
as you said it would free up a few whp most likely. as far as lift in cocern it really won't be a noticeable difference. the human body is not capable of measureing differences of only a few horses. technically it should speed it up--but don't get too excited because like i said its not going to be anything you can even remotely notice.
as far as landing in lift is cocerned..there will be no difference. the flywheel obviously doesn't raise your redline and it obviously doesnt generate lift at any earlier of an rpm. landing lift (without ecu modifications) is all about how you shift..your tach is gonna fall just as fast with a lightweight flywheel as it does with the stock flywheel in between shifts.