If we can conclude it's nonsense to say that other systems are more efficient than BTC because other systems aren't proof of work distributed ledgers, maybe it's also nonsense to say that Teslas are more energy efficient than something with a 6 litre V12 engine, because they don't have a throaty growl or run on petrol.

Back in the world of actual use cases, we can probably put a ceiling on the value of circumventing AML laws without using a non-POW altcoin at well below BTC's current energy cost.