ok so let me get this straight back then it was itachi clone with 30% chakra who can't use his MS and itachi clone succeed in delaying them, and with naruto help kakashi manage to outsmart itachi clone who even don't go for the kill,
and being compare to shikamaru who a lot younger than kakashi whose already experience a war and spend his time with minato namikaze whose also a prodigy,
is not really a good feat for him since unexperienced shikamaru can be compare with the man who a lot older and more experiance than shikamaru, surely by that logic shikamaru in kakashi age will be super duper smarter than kakashi himself
Kakashi is smarter in combat. He fights by analysing and outwitting his opponents through combo attacks, Itachi usually analyses and directly attack opponents weakness, doesn't use combos or make plans. I say combos require more brain power.
when itachi with naruto and bee fighting edo nagato he make great plan with poor intel about chibaku tensei from naruto, and before that he already calculated about nagato shared vision by disabling nagato summon with his kunai, surely that man is thinking while he was in action just like minato, and after the combination attack succeed in destroying chibaku tensei, he immediately pierce nagato with totsuka blade which is allowed since he already disable nagato shared vision.