I got the basic one (Bamboo) with the smallest possible size (I think it's the 4x6 one). If you're doing design and other complex tasks, it's probably better to have those large ones. For me though, since I only use it for general computing and the occasional design work, having a small one makes it portable (and it fits on my desk!).

Unfortunately though, after years of getting used to the mouse, I do find it hard doing detailed work in Photoshop (i.e. tracing something/colouring something). It probably has to do with me not being used to the tablet but in times like those, I (using the tablet) still don't have the dexterity to manipulate things as well as when using a mouse.