Personally, cutting the rig loose would likely not cross my mind as a valid option unless it's already down, because Todd's right. A mast flopping around in the waves, semi connected to the boat is just asking for holes in what little hope you have of not being a swimmer.
I agree on the rig as well. It would not be a good idea to drop it on the water. Besides the significant risk of damage, unless you have a rig specifically designed for it, it will be unlikely you could ever stand it up again unless you get to shore.
