I get the impression that there are quite a few YCers that didn't make it on the first application. PG has said in the past that the most compelling argument y

I get the impression that there are quite a few YCers that didn't make it on the first application. PG has said in the past that the most compelling argument you can make to investors is that you're going to keep forging ahead, with or without them. At the end of the day, YC are investors too. It would seem like the best approach would be to apply with a better version of your original app, because that illustrates that you are persistent (you weren't just looking for an idea to get in with) and can improve upon the initial concept. Best case scenario, IMO, your idea is the same but with more traction (I'm assuming of course there is/was a prototype involved).