Because Apple controls the hardware, they only have to design their software for the hardware they release to the market, versus the nearly infinite number of hardware combinations windows has to account for. There is some truth to this, but it ultimately comes down to how well any given computer design has been tested by the manufacturer (which determines the robustness of the device drivers) before it leaves the floor.

XP was the first version of windows to offer comparable performance to mac's OS offerings of the same era in this category. Vista has been a huge step back because they crippled it with what I refer to as sociopathic levels of DRM (which goes all the way down into the hardware level - we're not just talking encrypted media here).

Before I spark a mac/pc war, I'll note that only a subset of mac fans are deluding themselves - there are certainly legit reasons to go for mac products.

you are the media you consume.