HTC One M8 Windows vs Android Battery

Same phone hardware (except maybe LTE frequencies)

HTC One M8 Windows vs Android Battery Wars - SlashGear:
After 1 day, 2 hours, 41 minutes
Android HTC One: 68% battery
Windows HTC One: 81% battery

Does the HTC One M8 have better battery life with Windows Phone? | News | TechRadar

Android is based on Java (clone) VM, maybe not as efficient as Windows WinRT (native code).  Next version "L" may improve that...