One big difference is that Mastercard charges higher merchant fees when you use a World Elite vs. World card. http://www.mastercard.com/us/merchan...d_Criteria.pdf

This is, at least theoretically, to support the assorted "benefits" linked by mia. However, most of those benefits require using their travel agent... so are you really saving anything?

Aside from that, the few items that looked possibly useful were the 1-year free National Executive status and permanent(?) Sixt Platinum.