Strange, both models do 10 hours playing video when tested on a leading Dutch tech site.
Certain apps aren't very good when it comes to power management, apparently the Microsoft apps like Outlook keep switching to the power hungry dGPU when the iGPU is more than capable of handling the job at hand. I would recommend to keep an eye on these apps and when necessary turn the auto switching for the GPU off to force the use of the more energy efficient iGPU when doing casual things like browsing, email, watching video, etc.