It could be the pilot-versus-engineer difference. Maybe mere size: the 767 was built in the Big factory in Everett, while the 757 was down in the little factor

It could be the pilot-versus-engineer difference. Maybe mere size: the 767 was built in the Big factory in Everett, while the 757 was down in the little factory in Renton. Knowing engineers, it could well have been some minor technical detail that no pilot or passenger would ever see. Of course, the 767 performs pretty well even when underpowered! https://en.wikipedia.org/wiki/Air_Canada_Flight_143 https://en.wikipedia.org/wiki/Air_Canada_Flight_143