When 你 make 爱情 你 involve feelings, LOVE, passion. When 你 have sex 你 just have sex, without 展示 your feelings for the person, with no affection, with no sweet words 或者 whatever, that's just sex.
Well both are pretty much the same. Making 爱情 can be also be 接吻 and caressing other than intercourse and it also can be others like oral sex and anal sex (especially for 女同性恋 and homosexuals).
