Advantages are they stay up longer and support the arrow through more of the launch giving better flight. They put no tension/pull on your cables which can affect your tune and arrow flight.
They require no setup other than bolting them on, leveling and attaching to the limb. They do not have to be timed and you dont' need to worry about vane contact. No need for serving and splitting cables, very handy if you have a failure on a hunt.
Good topic, as I've been contemplating the same thing recently.
Tell me where I've flawed here, but one argument against a biscuit is it supports the arrow longer, therefore any torque or other flaws in form are magnified because of that. Could the same be said for a limb driven rest then?
Limb drivens definitely appear to be more simpler. And I like simple, especially if I'm giving up the biscuit.