Regarding the he said/he said stalemate argument, while that is a fair observation, would not Congress reasonably ask for what reason Comey would lie in the memo? All FBI agents are told and expected to make contemporaneous notes in investigations. By all accounts, Comey has done so throughout his term as FBI director. It appears almost certain that we will learn shortly if the memo exists, since it appears certain Congressional committees will see the actual memo in question. If Comey's memo says what it is claimed to say, exactly why would Comey sit there writing his memo, while saying, something along the lines "although the President did not request that the agency drop the Flynn investigation, I am going to say that is exactly what he said". Now, why would Comey do that? Why would Comey make that up, or should I put it, why would Comey lie about the conversation?
As of now, we have Comey friends/associates stating that during a private dinner with Trump, Trump asked Comey if he would pledge loyalty to Trump. Trump States as well that he asked Comey if he, Trump, was under investigation. In a claim disputed by Comey friends/associates, Trump claims Comey told him on 3 occasions that he, Trump, was not under investigation. Comey associates are adamant that Comey never said any such thing. And we have Trump warning Comey that he should hope there are no tapes of their conversations. And through his associates, we have Comey replying he hopes there are tapes, and that "that would be perfect". No doubt because Comey knows any tapes will show Comey in a good light. And we should fully expect a supeana for Comey memos will produce much more then just the memo revealed in yesterday's NY Times scoop. Comey made memos after all his conversations with Trump, apparently. Trump, on the other hand, referenced the possible existence of tapes that would back up Trump's assertion then none of these assertions by Comey are true. But, if Trump cannot or will not produce that possible countering evidence in a he said/he said situation, why would Congress conclude that Comey is simply making it up?
Trump asks for loyalty from Comey, and gets only a promise of "honesty".
Trump asks Comey to drop the investigation of Flynn, and obviously, that never happened.
In an interview with Lester Holt, Trump state's the his state of mind when he "decided to just do it"(fire Comey), was that Trump said to himself that "this Russian thing" was all BS by the Democrats upset that they lost the 2016 election. And he has continually suggested the investigation was just so much BS.
Trump fires Comey.
Putting all this together, why is Comey's memos, when all FBI agents are in fact trained and expected to create contemporaneous notes, going to be looked upon as suspect in their truthfulness?
Comey has one hell of a reputation for integrity. Witness his statements in the 2014 60 Minute interview of Comey. Witness his actions in the 2007 hospital bedside conversation with the Attorney General. Are we really going to expect Congress is going to conclude Comey now has no integrity whatsoever, and simply wrote a memo in which he flat out lied?