Deciding if you are for or non-profit can be decided later (add that to the application that you are deciding), but choosing non-profit might help your cause.
I also agree that choosing non-profit will most likely help our cause, it would take the company in a different direction. This is something we'd prefer to discuss with smarter folks (hence the desire to delay some of these decisions).
[1] <http://www.gravitycomputing.co.nz/joels-totally-fair-method-...
For the YC application, just say that you are not incorporated yet and that you are thinking of splitting 50/50, that should be good enough for them to review.