Its a matter of who makes the first mistake. In my opinion, Jiraiya has huge and ample amounts of chakra to supplement himself throughout the entire fight, and prolong it such that Izanagi runs out, and afterwards, Jiraiya will win.
However, Danzo has Shisui's Sharingan, which has KA, something almost impossible to deal with.
With KA, Danzo, otherwise Jiraya. Even if he can revive himself with Izanagi, his offensive attacks were really weak and maybe jounin level not more than that.
however without KA then j man because j man has plenty of stamina for izanagi plus elemental advantage and has more summons and with danzo and izanagi j man could defintaly get into sage mode