It changes the behavior. If I'm summarizing correctly, the farther right you go along the AI scale, the more aggressive they become, and the farther up you go in the scale, the more "smart" or tactical it becomes. So a determined AI will very effectively charge you and push you back, and a cautious AI will be more laid back, and easier to attack. Those being just two extremes. Hopefully I said that right, I'm still not sure about the mechanics either.