Were it a fight to the death, Sasuke would win. In that particular situation. For one thing, they fought in an enclosed area, and Sasuke can spam Enton without breaking a sweat now. He would've immolated the entire cave while protecting himself with Susanoo. Kabuto can't use Muki Tensei or Haku Geki without Sage Chakra, and he has to gather natural energy before transforming. He'd be burned to sinders before he can unfortunately.
The one chance he'd have is to use Tayuya's Genjutsu off the bat... which potentially can't even be done without his Sage Transformation. I mean, he still has the DNA and snake umbilical chord... so maybe he can do it. But I'm positive Sasuke'd escape it.
So yeah. Sasuke'd win in that particular encounter if they both were fighting seriously.
The one chance he'd have is to use Tayuya's Genjutsu off the bat... which potentially can't even be done without his Sage Transformation. I mean, he still has the DNA and snake umbilical chord... so maybe he can do it. But I'm positive Sasuke'd escape it.
So yeah. Sasuke'd win in that particular encounter if they both were fighting seriously.