I personally have been using both systems for multiple years; Windows-PCs since the 1990s and Macs since they started making them with Intel-CPUs. I've seen the best and the worst of both worlds. There is a ("best used for") time and a place for both of these systems, and I'm not dissing either one of them - in fact, I freely admit that you can DJ with both systems. However, as for the current state of affairs, my opinion is clear; for DJing, you should go with a Mac. As for the reason "why?", well - let's take a look.
System design objectives
This is something that generally is not considered by people deciding to get a computer, but it is rather essential. Windows is designed to be a workhorse for all sorts of activities from everyday Internet & office-use to gaming etc. whereas Macs are more targeted for professional work (granted, there are exceptions to this, but I'm just trying to keep this simple - even at the expense of oversimplifying things).Windows is in underdog position here, since their software needs to run on every hardware environment imaginable. In the Mac-world, there is a distinct benefit that all of the hardware-configurations (I'm mainly considering laptops here, but mostly the same goes for desktop-Macs also) are pretty much controlled by the same company that is creating the operating system. This means that software developers only need to test their code in a limited number of hardware configurations - compared to Windows, where changing one component may have unforeseen repercussions. This naturally saves time and gives the developers a lot more time to streamline performance for just that limiter number of hardware instead of having to test and retest and redo all the tests performed previously after every change.
Furthermore, since the Macs are more targeted for professional - rather than "one-size-must-fit-all" - work, the system architecture of the built-in drivers is very different. It shouldn't come as a surprise that just like generic software development, the Mac has a benefit in operating system (and driver) development due to the mentioned differences in the way hardware configurations need to be taken into account.
And finally...
You should consider that at present, Macs are built with Intel-based CPUs and generic "off-the-shelf"-type parts. This means that Your Mac can always be a Windows-PC, whereas Your Windows-PC most likely will not be able to be a Mac (granted, there are many Hackintosh-projects to do just that - to enable running OS X on a non-Apple hardware configuration - but setting one up will usually require quite a lot of fiddling up).So... like I said earlier, even if you can be a laptop-DJ on either of the systems, the most straight forward, easy and safe way to do it at the moment is with a Mac.
