Yeah, I don't think the EEPROM is blank - I saw a pic somewhere on the net of a very very old XDK dash on a real XDK xbox. (Trust me, it was an old version - the menu options weren't spaced out very much, and no icons for the games in the main launcher screen) In the settings window, there was something for EEPROM signature, and it wasn't blank, so there must been an EEPROM, especially if they even bothered to have that in the settings window.
(But the person who had this was retarded - You could see the XDK wasn't on a network and the guy obviously doesn't know how to take in-game 100% quality pics)
And about the extra 64 mb RAM, you'll only need that if you want to play / make games that are very memory intensive, like Halo1 and 2.
And don't XDK's also have a faster CPU? On a retail-converted-to-XDK-without-the-extra-CPU/RAM, the video tool is very laggy and doesn't even pick up sound. But it obviously works better on a real XDK - it would kinda defeat its purpose if it didn't.