We saw what Danzo is capable of. He is reckless with his Sharingan's. Thus making this fight go to Hashrima. I do see him being more calm and figuring out Danzo's plans. Plus I do see Hashi having more chakra reserves so which can come in handy. Danzo seemed to want to get close when fighting Sasuke even though he has limited range techniques. If he uses this kind of method Izanagi won't save him enough times as Hashi has a wider range.
... And it turns out the whole time that Danzo used KA on one of Hashirama's wood clones (which takes at least EMS to see through, as said by Edo Madara himself).
KA is from what we know, instant. yamato showed us mokubunshins as did madara. i doubt hashi could form seals faster than madara. even so, is KA even enough? with instant healing hashirama trying to kil himself would fail each time. unless he just told hashi to stand still while fuuton sword slices him up