If you have a laptop made within the last 3 years, chances are very good it has a card reader slot. Chances are also very good your desktop computer also has a card reader (or one attached via USB).
Using portable apps when bouncing between your laptop and desktop is convenient because those little cards stay tucked out of the way and perform well…
…if you have the right card.
Before continuing, for anyone that would ask why anyone would use an SDHC card when most modern software, files and so on can be synchronized via the internet, the answer is that the card is most of the time faster when used sneakernet style. While you couldn’t really sneakernet apps with floppy diskettes or optical discs, you can with SD cards. And given their compact size, they don’t stick out like USB sticks do.
Rule #1: Class 10 or better only
The best way I can give a mostly-accurate definition of the memory card classes is to compare it to USB 2.0.
While there are literal figures for what the read and write rates are for USB 2.0 and classes of memory cards, it’s the practical application that counts more than anything else.
USB 2.0 has an effective throughput of 35 MB/s. Most (but not all) Class 10 SDHC cards have a data rate of 30 MB/s. In practical application, USB 2.0 and Class 10 SDHC will “feel about the same speed”.
Concerning Class 10 with a UHS-I or UHS-II classification, these can supposedly outrun USB 2.0 speeds. Right now the UHS-I spec is readily available (Sandisk Extreme is an example), however it’s a toss-up whether or not in practical application it will be faster than USB 2.0.
Rule #2: Not all Class 10 cards are the same
On some Class 10′s the data rate is 10 MB/s. On others it’s 20 MB/s. And then you have the 20-to-30 MB/s range before you get into UHS territory.
The only thing I can say here is that you may or may not get good data rates, and to read reviews thoroughly before buying a card.
Rule #3: Digital camcorder guys do not exclusively dictate whether a card is “good” or not
Most people use Class 10 cards in devices such as digital cameras, camcorders and smartphones.
If a guy writes a review and says that the Class 10 card “didn’t work well in his camcorder at all”, that’s one to ignore because for all you know, it could be the guy’s camcorder that’s the problem.
The reviews that actually apply to you more than anything else are those that use the card in a smartphone, because they’re running actual apps off it – similar to what you’ll be doing.
SD cards are good tech, but you have to shop carefully
With USB 2.0 you can pretty much buy any pendrive and the performance will be roughly the same as long as it’s not some bargain-bin no-name thing (i.e. use Patriot or Kingston and you should be good in that department).
With memory cards, the data rate can vary wildly depending on what you get. From my reading of memory card reviews, Sandisk “Extreme” series (expensive) and Transcend (cheap) usually seem to make people happy the most.
But don’t take my word for it. Shop around, shop smart, read a lot of reviews and make sure whomever you buy from has a good return policy, because you may have to use it if you get a bum card that doesn’t perform as expected.
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Also noteworthy is the fact that some SD cards, particularly the ones that tout faster speeds (and are thus more expensive, like the SanDisk Extremes) have commonly been targets for fakes/immitations. Often buyers who don’t buy through a reputable dealer (and in some cases even then) end up with super-cheesy unofficial cards that are of terrible quality and accordingly have terrible speeds.
Long story short, don’t buy SD cards (new or used) from eBay or the like, and even when you do buy them, look them over and test them carefully when you get them to make sure they are legit. Often a fake card won’t have a serial number, but some do even have fake or duplicate serials. There’s plenty of articles out there to help you spot a fake, and contacting the manufacturer to verify your serial number might be a good idea, though at that point, it might be too late.