"trying to give the impression that 500 Startups is for plucky underdogs, and YC isn't."

Essentially he is saying YC is Hertz and 500 is Avis.

"Their corporate motto is "We Try Harder" It was adopted in 1962[4] (during the tenure of Robert Townsend as its CEO) to make a more positive reference of Avis' status as the second largest car rental company in the US, at the expense of its larger competitor The Hertz Corporation. "

http://en.wikipedia.org/wiki/Avis_Rent_a_Car_System

A well intentioned strategy of "attacking" (if you want to call it that) the market leader in the category. Doesn't even matter if they are really Avis by the way. Why? There is fresh kill on the internet every day. And those "fresh kill" are reading things like that and believing it.