DISCLAIMER: this is most definitely subjective and argumentative, but I've always wanted a place to ask this question, and now finally there is one.
Also, this is one of the example questions I submitted during the definition phase, and it got upvoted quite a bit as on-topic :-)
Psychohistory looks very much like a scientific evolution of Marx's Historical Materialism: social and economic forces shape the history, and the action of single persons just can't affect so much its outcome, even if that person is the Emperor of the Galaxy himself; this is of course presented not as a mere historical analysis, but as a strong mathematical theory... nevertheless, the basic concept is pretty much the same: there are strong forces that direct the evolution of every human society, and no single action can actually divert them from their path (unless some mutant guy with psychic powers gets involved). Killing Hitler wouldn't have avoided WWII, because it was just bound to happen anyway.
But then, The End of Eternity presents the exact opposite view: every single action is important, every single moment could become the point of divergence of an alternate history; killing Hitler would have avoided WWII, or at least directed it in a very different direction.
...or maybe, we are trying to make sense of all this, while we are actually just all in the hands of Stupidity, against which, as everyone knows,
"the Gods themselves fight in vain".
Back to the question: those two views of history are, of course, mutually exclusive... or are they? What did Asimov really think about this? Or was he just speculating in a direction just as in the other one? Are there other works (or other materials) from him that could clarify this issue?