It is only inefficient if you are raising them for consumption. If you for example are eating roof rabbit (cat) culled from feral cats, which are feeding on the rodent population you, are being very efficient from most standpoints, no? The cat costs you nothing to breed, it controls vermin until you need it costing nothing to feed and provides a source of protein. I would submit that it is probable easier to catch than a rat not only on a pound for pound basis but also on an animal to animal basis. Efficiency is relative but your other points are valid although taste is also a relative thing remember the kicker to this discussion is the fact that the Koreans are eating the meat not out of diving necessity but out of preference.