Distinction w/o difference. They're both feds.
That's it, after reading through this whole thread, I've determined that you're cracked.
And therefore neither has the authority to ban MJ (see that pesky tenth amendment).
At least the FDA will claim that they haven't tested it yet for medical effectiveness, and they don't plan to. They might not like the results. The DEA has no such half excuse, they are just JBTs committing crimes against innocent users and sellers of MJ and other selected substances.