Sex, or sexy? Because they are both different, but they both fit in the context. I desire to be sexy to others so that my desire to have sex would be fullfilled. However, as part of the Buddhist teachings of detachment, this is one of the desires of the world that must be overcome. Try to picture the object of your affection for what he or she really is. Flesh, which covers muscle, which covers bone, which covers blood and puss and bile and stomach acid. Now that this person is unattractive, you are no longer tempted.
If overcoming desire is not something tha appeals to you, picture the person naked and then go have sex with them. Either way, they are both good choices.