a 32 GB memory card will hold about 600-800 photos depending on the resolution, and whether you save the pictures in RAW or JPEG (JPEG are compressed, so it should fit about twice the amount). I personally have 2 32GB cards instead of a 64 GB, but my reason for this is that I use one card for a specific purpose (like family/portrait pictures) and the other one for another (like travel or vacation pictures). This way, I separate one thing from another, and also, in case the card gets damaged, the less amount of pictures you have in it, you don't loose as much. a 32 GB card holding 800 pictures that gets damaged is not compared to a 64 GB card holding 1600 pictures, you will end up loosing less. However, if you do take A LOT of pictures, and you take precautions (as in keeping the card safe or transferring the photos to a computer ASAP), then the 64 GB one will allow you to keep on shooting without having to switch cards. It all comes down to preference really.