lets do the former

Chances are that this was already mentioned but I read that promiscuity will eventually screw with your brain chemicals and bonding hormones that are released by having intercourse, especially among women. These hormones are the super glue that bonds people together and are needed to have long-term relationships. Also if it didnt work out with 40 other dudes and its always the others fault, chances are low that that you as the 41th will be her real prince charming and it will last. Would be to risky for me to invest emotions and time in someone like that.

Same goes for a women, you wont be able to tame the bad boy that had 30 different girls before you. Usually theres some sort of fear of commitment involved also check how the relationship to her parents and how her / his childhood was, usually theres something off

This ^^^