How to choose the best MicroSD card for your device

[Montigusto]

Hi Folks,

I have just been looking for the best option as far as MicroSD cards go. I can't remember where, but I remember reading someone's comment pointing out that max write speed is not necessarily a good measure of true performance for phones or mobile devices since usage also involves many random read and writes (unlike devices like digital cameras which would benefit a lot from outright fast write speeds).

So with that in mind I did a bit of research and found that SanDisk's Mobile Ultra microSDHC (Class 4) seems to be one of the best cards available as it bested many class 10 cards on random read & write tests. A 16GB card was tested: Round-Up: 15 microSDHC Cards, Benchmarked And Reviewed : microSDHC Cards For Mobile Devices
However that test was done in November 2011 and is the most recent that they've done. I've just been searching for that card now, and the only mobile ultra card I could find was an 8GB class 6, so it looks like things have changed.

But the point of that test is clear - Class 10 cards don't necessarily give best performance for phones.

So I'm just wondering if anyone has tried different cards, or do most people just go for a Class 10 as the default choice? I was looking for a larger card (64GB) and was going to stick with SanDisk, but the 64GB Mobile Ultra (SDXC) card is pricey (~AU$150) so maybe I'll stick with 32GB.

Anyway - I'm interested to hear peoples thoughts.

Cheers

Edited to add >> There looks to be interesting tests of various cards here: http://forums.whirlpool.net.au/forum-replies.cfm?t=1582172
That looks like it's updated fairly regularly and also includes some newer 64GB cards. Interestingly it seems like the older SanDisk cards perform much better than newer ones...

There's only four different 64GB cards tested there, three Class 6 and one Class 10, but interesting to note that the Class 10 card beat the Class 6 on both sequential and random tests. So perhaps the old theory of fast sequential speeds sacrificing random speed is not quite as true any more.

Another question that I may as well ask here - what format is best for 64GB cards? I have seen some posts on the XDA forum by users saying that they've lost data and had corrupted cards using exFAT formatting. Apparently this is especially true on Samsung devices which use a kind of half-baked exFAT implementation since they didn't want to license it from Microsoft? Or something like that? Anyone have comments to add about that? It seems like you've losing some of the benefit of a large card if you don't use exFAT and take advantage of 4GB+ file sizes.

A bit more interesting info (original post here):

The difference between the sdhc cards and the sdxc cards is that the xc are intended to be used on usb3 systems so that they can take advantage of the speed. This is important when you are loading the card with your music library or unloading it with your photos. (and you don't do it mounted inside the phone.)

A Sandisk 64GB sdxc class ten card won't get the 30mb read speed advertised. It gets regular class 10 speed, the gs3 has no speed improvements when using this type of mcard. Here's a speed test in the phone of the Sandisk 64GB sdxc I got the other day.

IME, exfat is sensitive to power level change and anything that stalls or disrupts any read/write operation. However, if the phone says that it is damaged, just put it in to your adapter and a pc with exfat support and run chkdsk /f (with the fix options selected).

However I just looked up a microSDXC card on Amazon and the description specifically states that if you reformat into a file system other than exFAT you may experience instability.

Other info seems to indicate that if you're using a custom ROM, you could get problems with the card not formatting properly? Also if you have your phone data encrypted, that may cause problems?

Seems like a lot of complications...

In any case I'm now wondering if all of this was for nothing if you're going to get a 64GB card... for example looking at the current offering from SanDisk on their website - all their 64GB cards are Class 10 anyway. :-\
It doesn't matter what class card you would prefer because there's no option? Maybe I shouldn't have even worried about it after all...