Sasuke easily. He more skilled with what he has. His speed is far greater than anything Kakashi has put out. His intelligence feats far outclass Kakashi's. If hyperbolic exaggerations is what it takes to grant him a win, then by means, do so. But based on facts? The man wouldn't last long on speed grounds alone.
He would've certainly beaten Hebi Sasuke, probably took Taka Sasuke and had fair chances against MS Sasuke. People on here only seem to understand power... skill, intelligence and experience are all just as important - with Kakashi holding a monopoly in all three, giving him quite an edge.
Hebi is very much like a less-refined and less versatile Kakashi, as evidenced when you compare their base stats of 31.5 to 34.5. Then you have to factor in Kakashi's genius IQ, his sense of smell that surpasses Kiba and taijutsu skill above Rock Lee. His experience means he also will more often than not, control the pace of battle too. If you want to understand the importance of skill and experience, look back to when Kakashi was playing in the same "power ballpark" as the Rikudous and Kaguya, in his DMS form... he instantly put the newly empowered Kaguya straight on the backfoot. Sasuke's power doesn't take a hike until attaining MS, but it wasn't till EMS that he completely left MS Kakashi for dust, power-wise.
Kakashi's intelligence feats are pretty mediocre. Until he doesn't produce anything at the level of Sasuke (which is ironic, as the plot has culminated), it's very difficult to take "intelligence" feats seriously. This is a complete non-factor against Sasuke, who is a prodigy himself. Furthermore, Kakashi holds no monopoly in skill, intelligence and versatility. You have overblown this greatly out of proportion, when his Raiton repertoire is outclassed as well.
Experience is all I would give you, which is quite irrelevant given that he hasn't produced any clever strategy that even matches Sasuke's, let lone something that makes one state, "he outwitted him." Thus, experience is irrlevenat, when it cannot grant you superior wits. It's just argumentation for the sake of it.
I feel that Kakashi's intelligence is always grossly exaggerated, when the manga has little evidence in its favor to put him at Sasuke's level. His best feat is Kamui's break down, and Sakura did the most work there. Really, it took him 200 chapters simply to figure out something so simple as "shared eyes." It's sloppy work. Something Sasuke would have no difficulty in. Therefore, that "edge" you speak of is hyperbolic is nature. Very hyperbolic.
In regards to CQC, then he was always on the defense against Hidan. A man with inferior reflex speed by his own admission. Versatility is absolutely in Sasuke's favour, who has more Raiton, Katon and extra Shuriken-Jutsu and Kenjutsu skills in his favour. As far as speed goes, then Kakashi couldn't even outspeed a Futon attack. His jacket was gone and he barely made it back to cancel out the Raiton tech from the mask; a element Sasuke far outclasses him in. He cannot manipulate the fingers to increase the potency of Chidori attacks as well. Something Sasuke can do with ease.
This is what I do not understand about Kakashi's favoritism. There is no canon evidence to put him on such a high pedestal. It's mostly hyperbole and what-ifs. And it always disappoints me greatly.