I can only assume you mean "by every conceivable metric", vs. "ever conceivable metric". Getting that discaimer out of the way in case I misunderstood you. With that said there is an easily conceivable metric (which is very highly correlated with BKO 8/10) by which international crews "work harder". That is of course block hours. A cursory glance at the May 757 CA bidpack vs. May 777 CA bidpack shows that most of the 777 lines have more block time than the highest block 757 line (Line 1021: 48:33).

In general its very difficult to specify who "works harder"...much depends on your definitions. In economic terms its often not relevent. The physical definition of work is force x distance. But even if you wanted to go with this physically pure definition, the 777 crews are still going to win, as they're moving a larger weight of freight (hence larger force applied) over a longer distance...therefore work done is going to be far larger.