I'm just assuming Kamui and Koto are out because the question changes to "who can get their haxed technique going first?" which is hard to determine.
With just base Sharingan it is difficult to determine how the fight plays out. While I certainly think Kakashi has the ability to figure out Izanagi, the problem is I'm not sure if he has the necessary tools to deal with it. Kakashi has always been the kind of guy to plan for an opening and then striking his opponent with perfect timing. Problem is with Danzo he forces Kakashi to play his game, which amounts to a war of attrition. Both characters react to Sasuke's arrow similarly so neither one seems overtly faster than the other so it becomes a game of tools. Honestly Danzo just seems to have better tools like Kakashi, particularly his sealing technique.
Take away Sharingan for both and the answer is probably Kakashi since Danzo has all of one fight to his name. Take away Sharingan for just the former since he was only ever Hokage with it and Danzo obviously wins.
Originally posted by Jmanghan
Ok, lets say we're using Kakashi at his best, k??
Kakashi at his best could momentarily rival Naruto and Sasuke. That Kakashi could take on a thousand Danzo without a care in the world.
Originally posted by Henry_Pym
in that fight Sasuke's used a bunch of shenanigans and a summon he never used to win. Without the Sharigans Kakashi gets demolished.
He also fought fairly brute-force, and had already used plenty of jutsu earlier that day- the kage kicked Sasuke around fairly well.
Note how Kakashi did vs biju with the lightning cutter between clones and similar powers.
And he's a lot more evasive than Sasuke, using underground and similar.