Which is more practical, a 350ml cup or a 500ml cup?

If you are still a student, buy 500 ml, because you don't have to drink coffee or anything, and it's inconvenient to fetch water all the time. If you are already an office worker, use 350 ml, because office workers often drink coffee and so on, and then often go to the water cooler and sit there for a change, which is good for physical and mental health.