Actually with intel sasori might know that he has to fight with puppets in front of him to cover himself from getting kamuied.
And while it's true that kakashi is a very tough opponent, he weakens pretty fast (low stamina) [he got recharged by kurama, at most he can do like 5-7 kamuis by himself]
And with that many puppets attacking at the same time it is kinda difficult even for him to aim perfectly at a moving sasori, let alone if he puts a puppet between him and kakashi's eyesight.
Poison is another factor too, remember that it might weaken kakashi right away if kakashi gets cut.
Both chars got a GOOD CHANCE, and it's not like everybody says that kakashi STOMPS.
Just my 5 cents.
ON A SIDE NOTE:
I bet everybody says kakashi, because of his flashy technique kamui.