As to which one is "better" that a subjective question. You can BOTH do an export & backup as they both have their uses
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A backup file contains certificates, while an export would not. An export is human-readable and largely/somewhat version and platform independent, but is it not the complete. They way I look at is use import to create a new router from an old one. But for stuff like being able to "rollback" a change, backup/restore is the way to go since all the MAC/.id etc will remain the same.
RouterOS doesn't enforce a version and platform checking on restoring a backup, so it will "somewhat work". But it's a bad idea. The benefit becomes the curse: since backup does restore MACs and other ID/certs/etc, that creates also sorts of associated problems from duplicates on the network. Similar with versions, it depend on how different the version and specific config commands were actually same. I believe cross-fig will still run upon a restore operation, so theoretically config would migrate from V6 to V7, but doesn't make it a good idea.
RSC is generally way to go, but it's not hard to always have the actual backup file too. If you need no-default=no to make an /sys/reset-conf file=x.rsc work (with a :delay in RSC
)... that sounds like a bug in the V7 export that it's not including something needed. Using
export verbose show-sen may be help, but make the config less readable (and potentially problematic since attribute name sometimes still are changing in v7)... Lot of choices here. Do several just in case