An Earth map wouldn't work

Nope, they are the same size maps. It has been said that everything except the presentation (graphics/controls) are the same on all the versions.
 
At least for the DS version. The world map is far, far, far too small. Plus the gameplay isn't suited for big landmasses.

Does the PS3/360 version have bigger maps?

360/PS3/DS all have the same map size. They also have only 1 map size.
 
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