Not neccesarilly, people still masturbate when they have sex. The vagina is highly stimulating to the penis, as it's only purpose is sexual reproduction, therefore sex would feel far better than masturbation. Something you need to ask yourself too, is it better by yourself or with someone you love? Personally I look forward to sex with someone I love, it wouldn't be good with anyone else. Although masturbation feels good, sex would be a totally different experiece.