Okay ... The smartmedia cards and MMC/SD cards are not the same thing.  The smart media card is physically large and will not fit into the DX3700.  The MMC or multimedia card has the similar idea of storing data but in a much smaller version.  The Secure Digital cards are identical to the MMC except that the secure digitals are designed more for PDAs for higher encryption of data.  I'm not sure of the technical specifications but in other words if you are just going to be using the memory for your digicam then I would recommend the MMC because the smartmedia won't work and the SD will work but at a higher price.