There was a discussion about this a while ago and someone had some evidence that showed our phone won't improve video recording with a higher (than class 4) rating, so transferring files should be your main concern there. I got a 32gb class 4
Micro SD and love it. No problema, plenty fast. But now a Class 10
is the same price as mine was when I bought it and I would buy it now. The 64GB SanDisk
out now supposedly does work in our phone even though our specs say it doesn't handle larger than 32.
I'll edit and add links when i get to a computer.
Sorry, can't find that discussion yet...
Here it is.