SD vs CF vs Memory Stick: Flash Memory Showdown

By Matthew Braga

Unlike the dark ages of flash memory, consumers today have a few, well-established formats from which to get their storage fix. But how do SD and CF really differ? And what's the deal with Memory Stick?

Unlike the dark ages of flash memory, consumers today are lucky to have a few, well-established formats from which to get their storage fix. But like the floppy disk, many portable storage formats have been phased out over time due to technical limitations and lack of consumer support (remember Olympus's xD format?). Today, most devices tend to use some form of Secure Digital (SD), Compact Flash (CF) or, if you're a Sony geek, Memory Stick. But physical appearances aside, time has done little to truly separate one standard from the next. Read speeds, write speeds and class numbers are thrown about like badges of honor, but what do any of these things really mean? Rest assured, there are differences. It pays to know what each format has to offer, and more importantly, the which format has what it takes to outlast the competition.

PCMCIA, the popular expansion port most commonly found in laptops. The advantage was that these small, CF cards could act as tiny, removable hard drives -- much like how the iPod Mini was designed, for example. With full ATA support, CF cards could appear as another hard drive to the host OS, bringing superior transfer speeds and reliability when compared to other flash solutions. 

newer CF spec announced this year says the theoretical capacity of a card can now reach a staggering 144 Petabytes -- good news for the photographers and filmmakers who still rely on these cards each day. Yet, all these features come at a price, and a 16GB CF card can often be double or triple the price of a smiler SD offering.

Class 2, 4 and 6 branded cards, with Class 10 cards announced last year. These numbers are much easier to decipher than the speed rating numbers of CF, and represent 2Mb/s, 4Mb/s, 6Mb/s or 10Mb/s minimum write speeds. 
But unlike their Compact Flash counterparts, SD cards lack a similar ATA backend and aren't commonly used as hard drive substitutes in devices or PCs. However, their size and relatively fast speed makes them a perfect fit for almost every portable device on the market today, from cameras to phones and even gaming consoles. Such proliferation has also made them the cheapest form of storage on the market. And although, the current SDHC spec only allows cards up to 32GB in size, a newer SDXC spec should expand that to 2TB.

up to 2TB of storage space possible.

In terms of speed, it's no wonder that Compact Flash cards are still used to this day. Despite their larger size, superior write speeds have made these cards particularly attractive for those shooting HD video or similar high quality content. However, SD's size and price has made it the preferred format for almost every mobile product on the market. And Sony? Well, their cards are still expensive, and still proprietary. But given the choice, at least you can determine which one is best for you.