OS X :: Windows So Slower At Most Everyday Tasks?

Most people here know that if you have two computers, both with the same hardware, and one is running Mac OS X and one is running Windows, the Mac is usually faster in most aspects. I know that Windows is, in general, a much less efficient OS, but specifically, why? I've heard that a lot of it is due to the fact that Windows will try to do 100 useless things if you ask it to do one simple thing, also I've heard that Microsoft wrote Windows by getting loads of people to go off and do different parts of the OS, then they would just paste it together rather than taking off the useless parts, fitting each part together and optimizing it. I just need a more straightforward answer as I will be using it in an essay.