I just completed same test on Redmi Note 5, both phones on latest MIUI 10 global stable.
Mi9SE 100-0% Standby time 4 days, 3000mah
Note5 100-0% Standby time 14 days, 4000mah
All same apps, all same settings, I made sure everything was equal.
Note 5 standby time is 350% but battery only 30%...