54 Wh
Apple MacBook Air (2017) 13.3" Intel Core i7 2.2GHz / 8GB / 128GB
54.5 Wh
Apple MacBook Pro (2017) 13" with Touch Bar and Touch ID / Intel Core i5 3.1GHz / 8GB / 256GB
Batteries with more watt-hours are larger and tend to last longer.
Battery size: is this important to you?