Is it better to break up in person or by sending a message?

It is better to talk to you face to face. If you have any misunderstandings or dissatisfaction, you can also make it clear. And if the other party is a girl, she may be very sad and angry after breaking up with you. She may be a little violent towards you, but vent it. It'll be fine when it's over. If you use text messages, it will appear that you are not serious about this relationship and it is too childish.