My full designation is YoRHa Number 9 Type S. That means I have the number 9 personality and my model is built with scanner functionality in mind. I share the same personality base as other models with the 9 personality, but we're different people. I'm not a combat unit so I would approach a situation differently to 9B, for example.

[Nevermind that he modified himself for combat anyway. But being able to fight is very different from being good at it. ]

You could say it's a bit of both. Humans adapt and change as they face situations and experience events, don't they?