You need power ? -> Tower PC with 2 i7's in it running Linux.
Gaming ? -> Windows (all trough it's crap in my eyes)
Editing/normal use at high quality ? -> Mac
Normal use -> Windows
I'm typing this from my 27'' iMac i7 and this computer is in my eyes better than my i7 Windows system. Just because it runs better. I bought my Windows i7 (and build it on my own) and it costed me 1200 euro's without screen , wifi , speakers , software (windows) , mouse etc. I bought it for video-editting , rendering , and photoshop etc. 2 months later my other PC for downstairs died. Well , it needed to be replaced anyways so I bought an iMac. And I need to say , I wished that I have had bought an iMac instead of the Editing PC. It runs everything , directly , always , fast. No need to instal 45.000 different drivers , nothing , just plug it in and you're ready to go. It costed 2000 euro's , but the specs aren't much different from my PC.
1200 euro PC:
i7
MSI Cyclone 4890 (oc)
MSI X58m
6 GB RAM
2 TB
2000 euro Mac:
i7
Ati Radeon 4850
4 GB RAM
27'' ISP panel <- This is in my eyes the very best of the whole system !
everthing build in
Amazing build quality
Better OS than Windows (OSX)
Timeless design
Keyboard
Very good mouse (Newest Magic Mouse)
1 TB
Death silence , no noise , no coolers , no big tower.
So , I don't think that it's not enough bang for your buck. I think it's even better than a Windows custom PC if you look at quality/price. Performance is something else. But for what instead of gaming and (extreme) calculating would you need to buy a Windows PC ? Price is lower , but that is something you will definitely see back in the quality and life time.
In the 4 months's i've had my custom PC , I had very very much fails , BSOD , driver problem's etc.
Mac's are just very very amazing for editing , 3D rendering , photographers , musician , artist , film editing.
For gaming , yes PC is the way to go. If you don't game , Mac is in my eyes the best. Or if you don't have much money , than the PC is the thing to get. BTW , i'm not someone that is Mac biased. The iMac is my first Mac , and it won't be the last. But even when it is a Mac , I will check if it is good. I don't just buy blind any Apple product.
Then there are some nice little things about the Mac ;
No viruses , not as easy as to hack a Windows PC , better OS design , works right out of the box's.
And honestly , the only reason to buy a PC in my opinion is gaming or the money.
I just don't see any other reason to go trough all the misery a Windows PC brought me many many times.
Hope my post make some things clear.