The only real advantage from an "unlocked" HG612 would be the more line stats info which also can be recorded and monitored through software like DSLstats, it could be useful and helpful in line diagnostics if something gone wrong with the connection (like huge speed drop, DSL sync. not stable, etc.. of the expected issues of copper based broadband services), although both devices probably use broadcom chipsets (I think the tp-link does use it) but tp-link blocks the direct SSH/TELNET access to the chipset and replaces it with a custom tp-link one which shows what tp-link likes to be shown, on the other hand the unlocked HG612 allows access to chipset so all the information about the line is available and can be accessed/monitored easily.