Second girl is easily better. Kicks are coming straight from her hips and she is trying to hurt him and is enjoying it. I would love to meet a girl like her
If you do it enough your balls become less sensitive to the pain (they fill up with scar tissue). Also, for hard ballbusting videos slaves often take painkillers in advance. I was on a set once where they even had an Entonox tank (nitrous oxide and oxygen mix) for the ballbustees to use during sessions.