Kakashi is superior in base. He has superior Taijutsu skill both featwise as well as statistically. He also has an elemental advantage as his Suitons counter Sasuke's Katons. They can copy each other's lightning attacks and probably cancel each other out, but again Kakashi's variants stem from the S-ranked Raikiri as opposed to the A-ranked Chidori so if anyone has the edge, its him. He is also more capable of pulling off in-battle feints thanks to hiding underground coupled with shadow clone usage, which Sasuke lacks. And while Kakashi doesn't have as many Mangekyo techniques as Sasuke does, Kamui is the faster trump card here so if it comes to a Mangekyo activation battle, its Kakashi's battle to win as well.
Oh, and Susano'o is not a clear-cut counter to Kamui. Not when we've seen early Part 2 Kakashi warp an explosion that was expanding omni-directionally and had just as much "depth" or "volume" as Susano'o would have. It didn't just warp the "frontal layer" of the explosion, but the entire thing. Kamui being used on Susano'o would be no different; the entire thing, from front to back (Sasuke included), would be warped. Not just the front of it.