All these useless comparisons about second segment, redundancy safety, hot & high performance, drift down over high terrain, blah blah blah...
Airline management around the world (and particularly in Australia) don't give a flying
about which one might be safest.
All these aircraft are certified to a minimum required standard, and therein ends their thoughts on it.
They choose the cheapest one. Period.
If you could build a six engine airliner with the same payload as a 777 which was 1% cheaper overall (considering purchase price, maintenance, fuel efficiency, staff costs etc. etc.) the 777 would go the way of the dodo faster than you could say "Here comes another management bonus".