I searched through several threads and could not find a definitive answer to the following question: what exactly is the difference between Emerald Executive (i.e., the level achieved through 12-24 rentals in a calendar year) and Executive Elite (i.e., the level achieved with the 25th rental) other than Executive Elites earn a free rental day after five rentals instead of six?

Is there a guaranteed upgrade to a non-ES/EE vehicle involved? I have seen parking spaces at certain stations designated as Executive VIP or some such - is that referring to Executive Elite?

Sorry if this has been answered elsewhere, and thanks.