I apologize for any misunderstandings. I meant "right before" or "just before" instead of just before.I'm assuming that the "regenerated" state is the state of the individual before their last battles were fought.
For example, if Sandaime could be revived, he would be revived in a physical state just before he fought Orochimaru at the stadium with an after-death mentality. This is applicable to Kakuzu, who would be revived with all of his five hearts in tact before he fought Shikamaru, Kakashi and Naruto.
I agree with some of your points. But maybe, I can shed some explanations of how Jiraiya compares his younger self with Hanzo through perspectives of reminiscence.Other than by the fact that his opponent is regarded by Jiraiya as extremely strong, even if he only beat 3 sannin when they were young. Jiraiya was in fact surprised when he learned that the leader of Akatsuki took him out all by himself. Nothing has lead us to believe that Mifune is anywhere near that powerful. Yes he is the leader of the iron nation and the samurai, but not all leaders are ridiculously powerful; the 4th Sand Lord had his ass handed to him by Orochimaru. Nothing has lead us to believe Mifune is as strong as a legendary title. But again, powerlevel scales are complete shit this arc. My ass Darui could handle two brothers who could compete against the 2nd Hokage.
For example, if you can recall earlier in your life, there must have been a really hard test you couldn't do very well at the time (say, maybe a basic algebra quiz). However, if you could write the test right now after studying the same topic for years (like majoring in maths), it should not be as hard to do as it was before. This should prove applicable with years of training and fighting practiced by the three sannin.
Orochimaru never had access to his full arsenal of forbidden techniques, Tsunade never had top-notch healing abilities as she does now and Jiraiya might have been missing a few key signature techniques that we've seen up to this point when they had fought Hanzo. Not only that, there's also the fact that these three, as adults, did not have as much wisdom and experience as they do now, which is a key factor in deciding the winner of matches.
My opinion still stands. There is no way to tell who's better if we haven't seen both Hanzo and Mifune in actual battle.