I like the sha-1 hash for comparing contents.
If you save the sha-1 has for the RData file, then reading it is just a few bits.
If you have a computed sha-1 for memory, then when you go to save, you can compare the sha-1 of memory vs. the sha-1 of what is on disk. If they are the same, then you do not need to over-write.
It should speedup the shutdown and shutdown-restart when changing settings. If someone is changing or testing through the settings several times in a row, trying to fine tune them, then the save-reload lag can be more apparent and uncomfortable.