I'm sure you're right, but it bothers me when the quality brand Class 6 cards on Amazon are 50% more than the Class 10 cards. Also if speed is the problem I'd rather NOT have a "fast" Class 6 that passes the threshold.
Still not sure what to do... going to ping e-prance about a possible firmware flash and report back.
HF
E-Prance AFAIK don't have any magical fixes, the 20130913 is their latest version for camera's with GPS only, and 0922 is their latest for cams with GPS & 8GB.
Just buy a cheap but good brand class 4, and all should be good. These cams write at approx 17200kbps which equates to 2.1MBps, a good class 4 should write at 4MBps or IME even 5+MBps, so in theory a class 4 is plenty fast enough. However, as I've stated many times, when the card fills it will then need to continually delete files to make room to write more, and I do suspect it's this re-cycling where it needs to delete files is where you need that extra speed headroom, as I feel it must impact greatly on the cards ability to write it's files fast enough to keep up. The write speed capability of a card given by manufacturers will always be it's 'Continous Write Speed' when the camera starts to re-cycle it's no longer able to write continiously, as it has to stop writing, and then start deleting, and AIS this will have a big impact on actual write speeds you actually get.
On checking Amazons prices this morning, I agree prices of the class 6 do seem inflated a little as you can get class 10 cards cheaper, But are still within a couple pounds of other cards on Amazon UK. I assume it's because they no longer make them, I suspect the reason they are a little more expensive is because they use better quality memory to achieve their faster speeds. Another important factor too is the fact that all these cards have a tiny controller file system chip on the card, so the efficiency of that will likely have some bearing on the writing speeds too, infact some SD cards also have built-in wifi capability too AYK.
Remember, class 2 class 4 and class 6 all use the standard bus/clock speed. which is the most compatible, and is probably why the manufacturer printed that statement in the camera's manual.
In theory of course, all the cards should be backwards compatible, but in use.. who's knows..lol
Class 10 cards primarily achieve their boost in speed by having a faster clock speed, the latest superfast UHS-2 cards have a even faster clock speed. It's no different than simply overclocking your PC's memory, if the memory chips used are not good enough then some will not overclock very well and will return errors. Overclocking the bus/clock speeds is a cheap way to achieve faster speeds, it's only successful if the memory chips and the controller chip used are faster enough to run at those speeds.. There has been extensive discussion on this subject in the main mini 0801 thread, MANY TIMES...lol