I've got a 16GB microSD card that I primarily use in my phone for local music playback. It's about half full - I really only keep my most recent music picks and a workout playlist on it, and stream everything else. Which brings us to a bit of a hiccup given that this is a review of a 64GB microSDXC card. In our Android-specific case, do you really even need a large amount of storage now that you can stream just about everything and anything on your Android device, and most ship with enough on-board storage to satisfy the app space of all but the most insane power users?
Well, actually, yes. There are three main reasons for this: wireless speeds, bandwidth caps, and coverage. Sure, the ability to stream movies instantly from just about anywhere is cool in theory, but what happens when I'm trying to do it while in the car on a 500 mile trip? Can I maintain adequate download speed the entire way to ensure proper playback? Probably not. And if I do manage to, I have a pesky bandwidth cap to worry about before I either get charged overages or throttled back to the 1980s. Alternatively, my WiFi-only tablets obviously have no cell coverage, so they definitely can't stream while I'm traveling (tethering excluded for the reasons listed above). All this is excluding power users (with their hundreds of apps), and the obvious non-Android use cases, such as with digital cameras or camcorders, where more storage means more pictures or videos.
Trust me when I say: even if you get a card that is 4x larger than you think you need, you'll probably still utilize a lot more storage than you think. Part of it is that you realize it's just flat-out more convenient to store stuff locally rather than streaming it (and in the case of a 64GB card, when I say "stuff" I actually mean "almost everything you could ever need on your phone"). The other part is just the sheer luxury of having plenty of space; you no longer need to consider "which playlist would I rather listen to" or "what movie am I going to want to see more?" Instead, it becomes "hell, maybe I'll throw a few movies on here for the kids to watch in the car" or "you know, I think I'll just put every album I've downloaded in the past 6 months on here."
At $100, the SanDisk 64GB microSDXC Class 6 memory card definitely falls more under the luxury category, especially when you consider that a 32GB microSD card can be had for a street price of about $25 - a whopping quarter of the price. But, again, if you can afford to splurge, you probably won't regret having all that space once you take advantage of it.
Not only does the aforementioned card open up a whole new world of portability, but it also packs some speed compared to its less well-endowed brethren. For those who don't know, speed class ratings determine the minimum write speed of a card. Thus, my 16GB class 10 card should be faster than the 64GB class 6 card I'm reviewing here. Let's take a look at the benchmarks.
My 16GB class 10:
The SanDisk 64GB class 6:
Rather depressingly for me (though good for SanDisk), the higher capacity card is also faster across the board despite its lower class rating.
There's a second concern here beside speed, though: compatibility. See, not all devices support the microSDXC format. Newer gadgets should, but the more dated your tech, the less likely it is to support the standard. My Galaxy R (the Tegra 2 variant of the SGSII) supported things just fine (after I formatted the card via my phone's storage settings), as did the Prime (again, it didn't work until it was formatted properly), and we've heard accounts of mSDXC cards working in devices that reportedly don't support them. In other words, check your specs and purchase at your own risk.
One last note about compatibility with Android devices: as mentioned, you'll have to format the card from within Android. Make sure you yank off the files SanDisk pre-loads on the card before you format it, because otherwise you'll lose them. (Common knowledge? Sure. But some people are silly enough to forget these things). The most notable file you'll want is the ready-to-roll version of SanDisk's Media Manager, so that you can just run it from the card rather than having to install it on your PC.
To put it simply and directly: the SanDisk 64GB microSDXC card has capacity, speed, and features going for it. Just about the only shortcoming is the price; then again, while $100 is a fair chunk of change, it's not unreasonable for what you're getting.