Well, specifically, they’re promising battery life that beats Qualcomm’s implementation of an ARM laptop SoC.
Qualcomm is significantly behind Apple. I’m not convinced that the ISA matters all that much for battery life. AMD’s x86_64 performance per watt blew Intel’s out of the water in recent generations, and Qualcomm/Samsung’s ARM chips can’t compete with Apple’s ARM chips in the mobile, tablet, or laptop space.