The gain isn't negligible when trying to squeeze all of that data into something like a Dreamcast VMU.
My JoyMenu mod (and iirc Makaqu's progs.dat too) has tons of optimizations to limit the number and size of the QC fields stored into saves. IIRC, some saves had their sizes cut in half thanks to this (or maybe it was due to the combination of Makaqu's progs.dat + engine optimizations - I really don't remember it very well, it was many years ago).