12h
Apple MacBook Air (2017) 13.3" Intel Core i5 1.8GHz / 8GB / 128GB
9h
Apple MacBook Pro (2015) 15"
9h
Apple MacBook Pro (2015) 15" Intel Core i7 2.2Ghz / 16GB / 1TB
9h
Apple MacBook Pro (2015) 15" Intel Core i7 2.2Ghz / 16GB / 512GB
The device's battery life (when in use) as given by the manufacturer. With a longer battery life you have to charge the device less often.
Battery life: is this important to you?