Itachi really meant it when he said that (him + Kisame) < or = Jiraiya, other thing that makes me believe that Jiraiya > Orochimaru and Jiraiya > Itachi is that high chakra reserve ninja are advanteged against low chakra reserve ones like Oro and Itachi,
Oro and Itachi should quickly try to end the battle which is impossible against a ninja like Jiraiya so as long as the battle goes Jiraiya will have bigger chances to win it.