I personally prefer Windows 7, the next updates have underwent a lot of drastic changes, that I can't seem to familiarize myself up to now. With the line of work we have, it's better to have an operating system that everyone is familiar with, so we'll be able to process our tasks in time.
I find that Windows 8 is the easiest to navigate, although the majority of people that I know in real life complain because they find it way too complicated. Most of them prefer to use Windows 7 despite the fact that they still have their beloved desktop.
I like all of them really. I have used OSX for photo and video editing. In the past, I have used Windows 7 and 8/8.1. I am currently using 8.1 and I like it so far. For the most part, I have disabled some of the metro features that come with Windows 8 as I find them very counterintuitive with a mouse and keyboard setup. I am waiting to user Windows 10, however!