both, obviously. sex is what makes you choose the most attractive partner. and love is what makes you stay.
think of it like a cellphone. every year theres a new cellphone model, and its always better and more more beautiful than the old model.
but some people get attached to their phone. and even if its an old model, they love it because it has served them well or it has sentimental value.
so love and sex work kinda the same way.
sexual attraction is what makes you choose the best partner. if youre buying a new phone you will always choose the best phone.
you will never get a cherry mobile if you can get an iphone.
love is what makes you stay. its like having a sentimental attachment to your old phone.
if you dont love your old phone then you would be upgrading your phone every year.
so in a relationship you would also be changing partners alot, because theres always someone younger, prettier, or sexier.
and thats why you really need both love and sex in order to make a relationship work.