I can argue both sides of declassification, both pre and post. BUT would really love to call Comey out on his public testimony offer if declassification is before. Though the whole five minutes back and forth, giving time to the hysterical left to grandstand, so far, is not helpful at all.
Pre pros:
-cannot cite classifed, can't answer
-can be public
-harder to spin and lie
-committee will be well-prepared
-may be able to introduce past testimony of others
-transparent to public, can be televised
-accountability of testimony
-harder for MSM to falsify
Post pros: only thing I can think of is perjury trap.