Significance:
It's simple; assembling a PC capable of running Windows or Linux is perfectly feasible; assembling a PC capable of running Mac OS X, for all practical purposes, is not. Period.
One of the biggest advantages of assembling your own PC – called a 'white box' PC – is one of cost. Doing so can often be the cheapest way to get a computer, or offer a bigger bang for the buck. Albeit not always...
On one hand you're not paying for assembly, but on the other hand you're not getting any bulk buying discounts the large manufacturers will be getting in that you're only buying one of each. As such, check prices before assuming, not forgetting to include the cost of the OS and any ancillary bundled software. And if the difference is negligible, ask yourself, is it really worth the hassle?
What hassle?
It's not that difficult, it has to be said. Many do this for the simple enjoyment of doing so. Okay, you'll need to know what parts are compatible with each other, but as long as you know what you're doing, the actual assembling should be straightforward. The hassle comes when it doesn't go according to plan.
What if it just doesn't work? What bit is it that's causing the problem? Or what if there's a niggling issue that's not quite right; say for example, there's a problem with the graphics. Who ya gonna call? You call the graphics card manufacturer, they tell you it's an issue with the motherboard you got. You call the motherboard manufacturer, they say it's probably an issue with Windows. You call Microsoft, they say it's probably a graphics card driver issue. So now what?
Contrast that with a pre-built PC; if it doesn't work , you go to the PC manufacturer and insist they sort it out. That's what you paid them for. Simple.
Okay, that's probably a nightmare scenario. But don't let anyone ever tell you home-builds are risk free. They're simply not.
Although there is a 3rd option. There are hundreds of independent PC specialists who will assemble a PC for you from off the shelf parts. They might be a little more expensive than doing it all yourself, but at least they're (hopefully) knowledgeable, and if it goes wrong, it's up to them to sort it out... just so long as they're still around to do so.
So...
...back to the original point, it simply comes down to priorities. If cost is your overriding concern, and you enjoy the 'tinkering', then the DIY PC can make a case that is hard to ignore. But if you want the qualities of tight integration that a Mac gives you, not least of which is the ability to run Mac OS X, then for all practical purposes, you'll have to forgo the DIY option and hand over your cash. That's just he way it is.
