I'm doing some tests with category.ini for MESS to filter arcade/non-arcade games in my frontend. I decided to use category_home.ini (MESS machines only) so the filtering works faster (2000 games entries instead of 31000 from the full .ini file).
I might even use version.ini for MESS to fill up version info field for MESS machines, since catver.ini from ProgettoEMMA is still at 0.161 and yours is updated more frequently.