We have seen what we can call the most we will see so far of the two but i want to know who would win in a fight. Now i don't want any biased opinions. I want this to be factual and support you claims that you are making. The both excel in Taijutsu the real question is who's Taijutsu will reign supreme and who will be the victor. No restrictions with anyone of there abilities.
In their base state, first things first...
- Gai isn't a dumbass
- Gai has a lot of experience
- Databook Fact: Gai has been over a lot of A-Rank / S-Rank Missions, even more than Kakashi
- Gai mastered the Eight Gates
Sakura only overpowers him in intelligence, with some luck.
This said, Gai can tank every move of Sakura, and Gai knows about Kai. Furthermore, if Gai is using the Eight Gates, then his Kai becomes more powerful due the improved flow speed of his chakra.
Sakura doesn't have any chance against him, even with Genjutsu.