SD vs. MMC: Which card is for you?

Size
Both MMC and SD cards are flash memory cards that're used with digital devices. Essentially, they work like floppy disks where you can save, store and transfer files to another device simply by inserting your card into the SD/MMC slot.

Weighing only 1.5g, these postage stamp-sized cards measure 32 x 24mm. However, the SD card is thicker at 2.1 mm compared to MMC's 1.4mm.

Being 0.6mm thicker, the SD card is probably more durable. However, the difference is so slight that when it comes to day-to-day use, the slight difference in thickness probably won't matter.

Speed
The biggest difference between an SD and MMC is the transfer rate. While an MMC can transfer data at a maximum rate of 2.5MB per second, an SD card can transfer four times as fast, at 10MB per second. Do note that these are the maximum transfer rates. Whether the card can reach that speed depends on the device using the card.

If you use a card reader to transfer files from a card to your PC, the difference in transfer speed is noticeable. But when using the cards with your Palm, the transfer speed won't make much of a difference since the Palm does not reach this speed during normal usage. However, we noticed that if you copy large files (about 4MB) to and from your handheld to the card, the transfer seems to be slightly faster with SD cards. Since you probably won't be transferring very large files in your day-to-day operation, the difference in speed is something you can live with.