W
If you'll buy 10 Class SD Card, your phone might start to having issues with regular work. If you're buying SD Card, get one that have saving and reading speed of +50mb/s. I have Sandisk Extreme Pro 32GB and it's save speed it +90mb/s. I had two other memory cards before that one - Samsung SDHC 64GB 10 Class which was making me mad. The phone was deleting the apps itself and my files. The save and read speed was 10mb/s. Another SD I've got was 32GB, 10 Class and same thing likeways with Samsung. If you are getting SD Card, get one that have very high speed of reading and saving and 10 Class.
I have a MS 535 and thinking of upgrading to 64GB.
64gb will be ok. My advice would be to get a sand disk. I got a samsung and trust me, it is a pain in the ***.
Have I mentioned anything about it? Just saying that higher SD cards speeds are working on Lumia phones.