This is not a comparison between OS X and Windows but the actual hardware. It is more of a rant than a comparison. Opening up a PC cabinet exposes a mess of wires, while opening up a Mac Pro cabinet will have you go "Wow, that sure looks neat".
The Lenovo cabinet pictured above is as messy as a non branded PC cabinet. They use pretty much the same components as any other PC. So what exactly are you paying a premium for? If you think only the low end PC cabinets are poorly designed, you are wrong. Even high end workstations like Dell Precision Workstation 490, which compares to MacPro in price is badly designed.
And Dell proudly showcases this picture on their Dell Precison homepage. To me it looks plain ugly and a pain to work with and pretty much the same as any other PC cabinet.
The MacPro design is both visually pleasing and practical. You can open the cabinet and change/install hard drives / RAM / Graphics cards or PCI Express cards without using any tools or messing around with wires. Good design is holistic. It is not just about being good to look at. Apple understands this. Apple installs extra large heatsinks on RAM to ensure "acoustic performance". Which other manufacturer cares about "acoustic performance" ? Most PC cabinets have fans blaring at full speed. Unless you like white noise, it is an irritant.
PC manufacturers really need to get serious about industrial design and move away from their insipid and uninspiring case designs with a tangle of wires. They need a Jonathan Ive of their own. While many PC companies do innovate on industrial design, it is usually limited and never becomes part of the company DNA.