I'm somewhat familiar with Faerun/Forgotten Realms thanks to the volumes of players guides I've amassed. Or at least I'm about as familiar as one can be for never actually gaming...I'm starting to think I must remedy that. While Ed Greenwood's world is great, it does have its flaws (if you care, ask a geek). I can easily ignore some geographical abnormalities as long as the story doesn't suffer for it. My issue with Faerun is that it has a really complex history, which is very understandable considering the run of its development. I like that though. Bring it on! Lots of history and mythos - my bread and butter.
Other gamers seem to like Eberron, but I know next to nothing about it. If I spent all my time and money buying up established world resources, my own fiddlings would suffer, and that I cannot abide.
Whatever your tastes are, you can't argue with the overall fantasticity and astoundingness of these maps
Eberron World Map
Khorvaire World Map
Detailed Khorvaire Map