Hello, was checking out advice for 21.5" iMac late 2013 upgrades for an SSD and memory (if it's open, why not?) and I'm doing this for my aunt whose iMac is running incredibly slow. She has maybe 1/10 of the hard drive being currently used so it might be going bad, it is the original unit. Question (opinion?) about memory; on Amazon they have the 8gb mention but I also noticed they had one that was unbuffered. This seems to be a bit cheaper but just a little. Any advantage or disadvantage to this one vs. what I presume is buffered? Thanks.