With older cats, you can tell what their adult personality and behavior will be like when you adopt them. What you see is what you get, generally.
With kittens, it's not so easy. I lived with three kittens who were such firecrackers that we had to buy those plastic coils through which you insert electrical cords to prevent them from being chewed. They grew up to be the most inactive cats I know with the exception of occasional fights and chases. (Which used to be not so occasional until the moodiest cat went on Prozac at the vet's suggestion.)