Overall, it all depends on what you shall be using the system for and what your occupation is.
Firstly, if you are mostly working on graphics or video editing, then gaining a Mac would be your best choice as you have access to more professional software which overall runs faster and has the ability to render faster.
Now, if you're mostly gaming or messing about online - Gaining a windows PC would be the best option as it would allow you to gain a number of games which are not available on other platforms whilst not having to pay a huge chunk of money.
When it comes down to your job, you need to balance out all of the factors such as what work you shall be doing, for example - I do Mobile Application Development and therefore I require both Windows PCs and my Mac's in order to work efficiently.
There is no 'best' system - It simply goes down to what you shall be using it for and which one works best for you.
. I have the most powerful iMac at the moment however hopefully soon I'll upgrade everything on my computer. Probably going to get Windows 
