The problem with a common /home that is used by different OS's, is, the many hidden "dot" files. In those files are the config data for your browsers and software packages, and if different distros have different versions, the "dot" files get all screwed up, and your software does not work as expected (or at all).
So, make a directory,
# mkdir -p /mnt/DATA
and in that directory make your data folders, "DOCS", "IMAGES", "MUSIC", "VIDEOS", "PROJECTS", and whatever. Mount that in /etc/fstab, in each different OS. Now symlink those directories to your ~/home/user directory in each OS, and you will have no worries about the hidden config files.