Sorry if the tonation of my post is to entirely shift your startup into focusing on YC. What I meant was, Working on a startup is the best form of education. If you land a deal with YC, that's even better, it's a way to decrease the number of errors you make along with the time it takes for you to succeed.
I agree that YC would increase your chances of being successful, but I wanted to encourage you that you can do it either way.