How does battery life compare with OSX vs Windows 7 (or 8.1) on an Macbook Air?
With OS X Mavericks, the operating system was designed with some focus on power management. The benefit of Apple making the hardware AND operating system is that they are able to control an manage power way more effectively than Windows is on any machine. It also depends on if you're using BootCamp or a virtual machine like Parallels or Virtual Box. BootCamp should theoretically be more power efficient as you aren't running BOTH OS X and Windows at the same time.