Either way, sex will be had. If it's not, and there's any sort of tension between you and your partner, you're gonna be rid of eachother really quick.
I honestly don't know that much from experience. I first had sex when I was a minor (14), with a girl from my Junior high school who had a reputation among the guys she thought were "bad boys". (I was doing campus duty).
Any how, since then I've only been in two other relationships. First one lasting 1-2 months, and the second one lasting 4 months. I didn't have sex with either of the girls, because I was the minor in the first case (15) and she was 18--and the next girl was the minor, while I was 18. But this type of thing is pretty obvious. A relationship without sex is like eating cereal without milk. It's just that there you have it, you know. It's very important. It comes second to love, but it is also what helps continue the love. Has anyone heard "Love is lust in disguise"? It's almost always going to be the case until the two people are over 30. Really, it's a maturity thing, too.