i would think that the difference would be the live plant vs the dead one. the live one can absorb while the dead one can release what has been absorbed.
I believe it is the cell structure that does the work, IMO this is why Gerson used the Norwalk Juicer. It treated all vegetable cells similar to the chlorella treatment allowing more enzymes and better detox.
But to put it simply, if you are going to try to detox then you need as clean a product as possible because adding chlorella or kelp that is already toxic won't do any good...