Think i would be tempted to go for one of the bigger manufacturers Sandisk/Lexar, saying that have never used anything but Sandisk so have'nt really got the gen to comment on the others,the way i saw it was that it seemed to be the most used by tog's Pro & Amateur so the majority of people can't be wrong.
I would rather pay that bit extra and have the piece of mind!!!
As for speed not sure what classes equate to but obviously the higher the speed the faster it will write to your camera and will be read by your computer....
