The answer to this famous riddle is, of course, that neither one is made of cheese.
The answer “Poe wrote on both” is popular, as is “they both stand on sticks” and “they both come with inky quills.”
The answer the Hatter admits is “I haven't the slightest idea.”
http://www.wisegeek.com/why-is-a-raven-like-a-writing-desk.htm