Frankly, there is no ‘Period’. It varies amazingly depending on what you want:
Apple- stability, but at a lack of options/customizability in software and hardware. And it’s only natively best for those OSes because Apple refuses to let other people touch their toys. But anyway…
And then the PCs, which, yes, can be less stable, but offer worlds more options:
Falcon Northwest/Alienware- yes, they’re not the same, but they give the same thing, damn pricy, but damn powerful, computers that are very well built.
IBuyPower- my personal favorite, still very good hardware and build, but significantly less pricy then the two above.
Toshiba/Lenovo- I’ve heard good things about both, nice computers without the power of those above but a little more use friendly, and much less expensive.
Dell/HP- good if you like really big headaches.