In fact, when he says "when you're slipping in and out of time,/who are you to decide,/which one of us winds up broken, for a lifetime..." he probably means the rival model is having trouble keeping up with the fashion trends (slipping in and out of time) but is more popular than the singer, who considers themself a better model or pop star. Since Jay is a fashion model anyway, it makes perfect sense!
In fact, when he says "when you're slipping in and out of time,/who are you to decide,/which one of us winds up broken, for a lifetime..." he probably means the rival model is having trouble keeping up with the fashion trends (slipping in and out of time) but is more popular than the singer, who considers themself a better model or pop star. Since Jay is a fashion model anyway, it makes perfect sense!