It really depends what you mean by “efficient”. But even if you go with “profit maximizer” that’s still an ideological truth that falls apart easily for most human endeavor. Since both organizations are made of the same kind of humans, have the same basic technology and access to resources (when not crippled in some way). When you add on top non monetary social goals, task more complex than “deliver commodity at lowest cost and max profit”, especially if you consider externalities, tgen saying " corporation are more efficient" as a blanket statement for use in all cases by default, it seems to me this is an ideological statement, really, an article of faith more then anything else.