I can't speak for the rest of the lineup, but I know that YC partners see hundreds of startups run through their program each year. The aggregate value of that is significant, and there are very few patterns they haven't already encountered.

Having seen so many iterations of the startup process, I'd argue that they are eminently qualified to give advice on the subject.

I'd certainly prefer it over some random, anecdotal account from a founder who just happened to be in the trenches recently.