Mac Battery Recommendation

A friend is contemplating upgrading from his 2017 MacBook Air to a model in the M2 lineup. As a frequent traveler often without access to a power source, he finds himself at a crossroads between the M2 Air 13 and M2 Air 15. The M2 Air 13 boasts a 52WH battery, whereas the 15 comes with a larger 66WH battery. Given his consistent practice of activating the screen curtain and maintaining a display brightness of zero, he's pondering whether choosing the 15-inch model would yield prolonged battery life. Despite both Macs purportedly having the same battery life as specified by Apple (since the larger battery on the 15-inch model is allocated to power the larger screen), he now wonders if, with the screen curtain off, he could potentially achieve even better battery performance on the 15-inch variant.