Since the war has begun, Tsunade has really started to show off all that she really has to offer, and I now believe that Tsunade is the strongest Sannin.
Earlier in the mange, Jiraiya admitted that he had only came close to death two times: When Naruto went ape shit on him, and when he crossed Tsunade for being a pervert, this shows that Tsunade could easily defeat Jiraiya if she caught him off guard.
Tsunade has also been shown to have the upperhand over Orochimaru:
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I think that in a battle now, Tsunade could defeat Oro, physical attacks won't work, but that's only for a limited time. Oro can only regenerate a few times before he exhausts too much chakra, shown when he fought Naruto in 4 tails mode, after that, he is vulnerable.
Tsunade is now fighting an holding her own against Madara, and now with the release of her new technique, she is pretty much unbeatable unitl someone pushes her to the point that her jutsu causes strain to her body, and I doubt Jiraiya or Oro could do that since it has yet to happen with Madara.
One more important statement is that Jiraiya displayed great power before he died, and Oro's power has been displayed throughout. Tsunade is still alive and showing us more tricks up her sleeve, I believe if she did die, she would have more to show, but as of right now, I believe she is the strongest Sannin.
:scorps:
