The X9 has has 3 different versions, X9, X9 Plus and X9 Max, each version has a different battery and is available in orange, white or grey.
All versions have a 500W, average power motor - so when deciding on what model to choose you first need to determine what range you are likely to need, then select the colour.
All models state the manufacturer's tested range. However please note that these were obtained in test conditions, so on the reduced speed setting, on a flat course with a 75kg rider and on a continuous ride. In reality most riders use the maximum speed setting, they go up inclines and most rides are start-stop. If this is your type of riding then an approximate range would be around 50-60% of the manufacture's figures.
When selecting the model and therefore the battery remember that a larger battery is heavier, takes longer to charge and is obviously more expensive.
You may find that after evaluating your requirements you are after a lightweight scooter, if this is the case then consider the HX X8 as this has a smaller battery and a 350W motor.