1st. It was Orochimaru who told Kabuto first hand in before the chuunin exams that he was 'almost at the level of Kakashi', as he was asking him to kill Sasuke, because Kakashi was said to be guarding him. Don't question someone so crudely unless you know the facts yourself, dude or lady.
2nd. This is a reply to the actual thread question, and Sakura was presumed in one of the first few Shippuden chapters to be 'well on her way to surpass Tsunade'<--*cough* Hokage *cough*
So, her and Kabuto were both said to be extremely strong. Now, healing wise, they are stronger than each other in different ways, Kabuto in his sick torturous ways, while Sakura is with the actual point of healing someone, and with her determination.
Kabuto is mainly a threat due to his tactics, and ways of foolery, but Sakura has seen through even Kakashi's tricks when she was only a genin. [Besides his Sasuke genjutsu, but that was back when she had no actual goal as a ninja and did not take it as seriously as now.] So it would be a close match.
I do not know who would win, honestly. Kabuto is very cruel and picks at people's emotional weaknesses, but Sakura seems to get stronger when reminded of her goals, i.e. If he were to pick at her weakness, being not being able to stop Sasuke, or protect Naruto and Sasuke, she would become angry and much more determined.
If it hasn't been noticed by most, the battles in this manga are won by the weaker ninja many times, due to that character's determination. Whether she is hated by someone or not, Sakura is very important to the plot line development, and at this point cannot die. So if this were to actually happen, based on the manga's way of putting things together, and way of getting a message across, I would say Sakura would be the winner.
Kabuto simply isn't as important, maybe as fusion Kabuto[current version, with Orochimaru] but not as his former self. He is merely Orochimaru's closest pawn, and can be disposed of without drastically hurting the plot.
Based on skill, I still do not know. We haven't seen Sakura fight, and as Sasuke and Naruto did when their sensei's from the legendary three died, she is well on her way to having her final development as a ninja.