Flash vs. SD Memory
CompactFlash (Flash) and Secure Digital (SD) are two common types of memory cards on which many digital cameras can store your pictures. The bottom line is that smaller, cheaper SD cards are fine for most point-and-shoot digital photography. If you have high-powered equipment and larger image files, opt for the larger-capacity, higher-speed CompactFlash cards.
Size
Flash cards have a 50-pin interface. SD cards contain between eight and 11 pins. This means that flash cards are fairly small, but SD cards are even smaller and lighter in weight.
Speed
Flash cards have read/write speeds of up to 90MB/sec. SD cards typically have read/write speeds of up to 15MB/sec. Some of the newer high capacity SDs (SDHCs) have speeds of up to 32MB/sec.
Capacity
The largest flash card in terms of capacity is 128GB. The largest SD card is 64GB.
Cost
SD cards are less expensive per GB of memory than Flash cards. According to PCWorld.com, for example, for about $41, you can buy either an 8GB SanDisk Secure Digital (SD) card or a 4GB SanDisk Extreme III CompactFlash card.
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