This is like the argument "Will it give me more pleasure or happiness?" Lust and pleasure are fleeting and easily attainable. Where happiness and love are long lasting, positive aspects that will never change.
It just a matter of if you're being honest with yourself when you evaluate the situation. Am I really happy with this person or am I just sexually attracted to them? Is it unconditional? At what point does he usually get bored in relationships and will I be like the rest?