On the one hand, we have people displaying facts from officially canonized works..
and on the other hand we have somebody saying "they don't matter, my impression from the movie was different."
Fact is. Movies are 100% canon, instantly. Yes, you can take different things from the subtleties of acting - but once a body of work from the EU is officially canonized, your impressions are secondary. The book is right, you're wrong.
Palpatine was more powerful. I don't like it either, but it's fact. It's canon. The book says that, in the battle, when Palpatine began to stop underestimating Yoda, he dropped his hold on the power that had been clouding the entire Jedi Order (including Yoda) ..the veil they couldn't see through.. and Yoda saw the "truth" ..that he could not kill Palpatine, that even if he killed this body, he'd rise again. There's clear yet subtle reference to Palpatine's ability to reanimate in another body.. Yoda saw the truth and knew if he were to do any good, it would have to be another way.
Yoda, being the pinacle of Jedi strength and understanding of the Force ..would not continue an unnecesary and effectively pointless fight, even if he could eventually physically win it. He knew all he had would not be enough to permanently end the threat, so he fought to survive and fled when he got the chance in the hopes of contributing to a better end in the future.
Was Palpatine a stronger fighter? That's not the point. It's not really covered.. what is, is that Palpatine had more POWER ..in the ability to reanimate with a new body and to twist the minds of the masses.. Palpatine could not be beaten by Yoda. Period.