Situation: have two boys and one 9.2 3DS, GW waiting to be awoken and waiting for N3DS release to purchase another one. What is the best way for the two boys to share the 3DS in order to keep saves/worlds and related stuff separate. Swapping out a micro SD and SD card every time it changes hands is not optimal but if that is the way it is, so be it. Right now the slots on the games seem to work, but they do seem to get in fights about some stuff, maybe it is x/y or animal crossing, not sure.
In the DL/DSi days they had separate systems and Acekards. Those died and they have been sharing a r4, with separate mSD cards, and sharing retail 3DS games except for x/y.