I believe Comey.
Trump tweets and White House statements provided several (sometimes conflicting) statements on why Comey was fired. My analysis is that if you need so many reasons to exlpain why you did it you're seeking excuses and not telling the truth. And Alan, this is not coming from biased liberal media, these different statements and tweets all came directly from the horse's mouth.
Trump stated he fired Comey because of Russia, that he refused to acknowledge publicly that Trump was not under investigation regarding any collusion. Just re-read all the posts in this thread by Jeff and others accusing Trump of collusion. This tied the presidents hands in dealing with Russia.
So you have a subordinate controlling his boss's action to do America's business with a foreign power. If Comey could revel publicly that Hillary was no longer under investigation regarding her email server, certainly Comey should have removed the false cloud over Trump a lot earlier than at his hearing yesterday. If he didn't want to make the decision to take the cloud away, he should have provided the information to the Department of Justice who he works for to make the decision. He deserved to be fired so Trump can now do America's business with a free hand.
As an aside, you can add to that his total mismanagement of the Hillary email server issue that even Democrats wanted him fired. As Director of the FBI, he had no authority to decide what should happen to Hillary. His job was to investigate. The department of Justice (Attorney general or her associate) should have made the decision whether to indict or not.
Now that the cloud has been lifted, expect to see more American discussions and meetings with Russia. We have to be discussing things with them. Creating a better atmosphere between America and Russia will benefit Europe as well. Two nuclear superpowers having tanks aimed at each other in Eastern Zeurope is too threatening to the world to have the American president's hands tied with limiting ability to negotiate. Don't you want to see things quieted down there?