Is a Class 10 MicroSD overkill or is a Class 6 adequate?
It is most likely overkill unless you are doing a lot of write/reads to your SD card for some particular reason.  The only reason I've known to buy a faster SD card is for photography, when you want to be able to reduce the time it takes to write photos from the memory buffer to the SD card so you can take more pictures at a higher FPS.