Being a user of both Mac and PC, and see both having their advantages. I personally would lean towards the PC.
Each and every time I need a new system I look at both players to see if there is something one has that would give me the upper hand, and at what cost. Now if one does have something, how much more is it going to cost me. It has become a lot easier to compare components now that Mac is using Intel, so it is a straight hardware comparison (excluding the OS and the very nice and super sexy Macpro case).
Now, Schewe, may be very right in that most if not all creative industries have the majority of their computer with a Apple Logo on them.
Why is that? Well, We are creatures of habits. Macintosh was the first computer or one of the first computer companies with a real sell-able GUI (Graphical User Interface), this enabled the then creative industries to use the Macintosh computers to improve their trade back then in the 80's+, MS-DOS back then wasn't even conceived at that time. Macintosh build up a strong following back then, and this Macintosh/Apple/Mac tradition has had a strong followed since in these fields. Hi, there is nothing wrong with a good Mac!
Bill Gates & Co came along, and it has taken many years for them to build some really good OS's, personally for me XP x64 was great (once I got all my drivers :-)), and now Windows 7 x64 seems really nice, its probably the first real answer to OSX.
Anyway, Windows took hold in the conformist (as Schewe points out) e.g. the business world (the guys with the money!) and managed to build what we see today, leaving Apple/Mac in the dust in terms of market penetration, some 90% or so of the overall computer market. Apple managed to get another strong foot hold in the Education departments, in particular the Higher Education/Universities with highly subsidized deal for them, and what better to do, then prime the next generation of workers and thinkers with the Apple/Mac philosophy. Its one of the few things that has kept their computer's going for them.
Interestingly enough, I don't know if you have noticed that Apple has removed "Computers" in their name (logo), and as of January 2011, have stopped their Server Division. No more Xserve!!! Though Apple isn't making their money on their Macpro, iMac or MacBook's etc... any more (not to say that they don't make money on them) but the core of Apples business isn't computers any longer, its MP3 players (iPods), phones and tablet's
What I really like about Apple, is their ability to design their products in a visual sense, its very appealing in particular for a Dane (Scandinavian), they are the B&O of computing and gadgets! Sexy, gorgeous objects! It beats me, why any PC maker can't do the same!
Anyway, getting back on topic here after this quick-step history lesson :-)
There are many people who in resent years have left Windows for OSX, and its interesting to see why they left, because they will often complain about their computers not working as they desired and this is interesting because where all Mac's are build to a given standard, and can therefor be judge accordingly, However not all windows computers are build equally and this is where we find that people will complain that computer XYZ with Windows on it, isn't working, it keeps crashing, even from well established vendors. Often such computers are build to fit a price-point, and compromises have to be made. This is an area that has served Apple well, that they have been able to maintain a "Turn it on! and it works!", well, ok it works most of the time!
There are also us creatives how do not wish to conform to any one, in particular not to a computer company that says, well, of course you can have choice, we have two graphics cards to choose from, pick one, but only one! (just one example! for simplicity). We want more then just 4 hard drives in our computers, and we want the fastest CPU and the fastest RAM, and that RAID card isn't cutting the mustard here, I want arrays with 8, 12 or 24 drives in various configurations.
Last time I checked, Windows XP x64 loaded separate profiles to each of my monitors, Vista did too (but i have to admit i didn't like Vista! a glorified service pack! a bit like going from one cat to another except it was more expensive!), Windows 7 seems to be doing it too. I am yet to connect all 4 monitors.
Damn, getting so sided tracked here, but one thing I do like about the Mac OSX is the column view in the finder and also that you can color code your files and folders! Why you can't do this in Windows is beyond me.
RANT OFF!!!
Anyway, to OP.
If you need advise on what to have in your Windows Workstation, I am happy to help you out. It is a bit of a jungle out there with choice (almost too many choices :-) ), but I am sure both the Mac and PC users, those who are interesting in high performance computing, and in this particular case high performing Digital Dark-rooms (All Digital Photography), we are on both platforms held back by the same bottlenecks.
That said, in a PC/Windows, not all components are equal, some brand, type are better then others. Some don't want to work if component B is there and so on, so its important to know what one is wanting to archive with their build, its very much like building a Hot Rod car, but in this case a computer. I think this process is why the 9% of computer user chooses Mac over Windows.
A high Performance Windows machine isn't cheap, it may be cheaper then the equivalent Mac, but we are moving into Medium format price land here, or just short off!
I personally consider anything with one CPU to be a Desktop system, and Dual processor (or greater) to be Workstations/Server, also if one is to compare Apple with Windows, and you are looking at a Macpro, then you will need to look at a Dual Processor system on the PC side. The advantage of a Dual Processor system is that you can add more RAM to the system, as each Processor has its own Memory bank allocated to them. You will also find that Workstation grade components to be more expensive and also more durable then their desktop counter-part, in some cases they can perform a little slower then their desktop equivalent,
However, when we start looking at workflow, the Dual Processor win's nine out of ten, as the they will perform better when you are multi-tasking and I believe this is the key.
The bottlenecks, CPU's are today pretty fast, and spend most of their life waiting for us, So we can count this one out.
Enough memory is important, it doesn't help you have 2 or 4 Giga-bytes of ram wish to process a 2 Gigabyte panorama and expecting it to be ready rendered in 10 minutes, it ain't going to happen. So having enough ram is vital for good performance.
These days a good graphics card with 1GB of Video ram or more is great, I currently don't know of any photo-related software that can take advantage of multiple GPU's or SLI/Crossfire yet, but its bound to come and I am sure that even though Apple doesn't currently support it, they will when the day comes.
Now, to the bottleneck!! Drums please!!! its your hard drives!!! Single drive systems are a thing of the past, it is preferred to have a single disk for you Operating system and your applications, then a separate disk for your Data/images. This would be a minimum configuration, the bare minimum!!!!
Today, if I were to build a minimum configuration of hard drives, I would do the following (for Digital Darkroom PC/MAC)
1 x SSD drive for OS and APPs
1 x SSD drive for Scratch/temp/page-file, this can be a smaller disk then the OS, but I would buy two of the same disks (I will tell you why later)
2 x mechanical hard drives for DATA, and I would make a RAID-1 (Mirror) for this, now I would recommend Enterprise grade hard drives here! Such as Western Digital RE-4, Seagate Constellation, or any SAS disks
This will give you a fast OS/APPs it will load your applications quick, if in Photoshop, the scratch disk will be quick. You data will not be as quick, but it will have redundancy and though not a backup solution, its the next best thing. Obviously one should have a backup solution separately.
To Jazz it up a bit, I would double, triple etc... all the drives i RAID-0 (Stripping), this will require RAID or HBA controllers, which are additional to what you computer comes with. This will significantly improve the speed of the computer, because it will suddenly be able to move the data/image between devices much faster.
To give you an example, and average hard drive will on average move around 65-75 mb/s, a good one above 100+ mb/s, SSD (sandforce based) will do 170-270 mb/s, Crucial's C300 will do 250-340mb/s give and take 10% here on all numbers.
in my current system, with 3 SSD's for OS and 2 SSD's for Temp/scratch and 4 HDD's for DATA, here I will move data on average 350-500mb/s and in bursts of up to 1.4 GB/s now my own plan is to double these numbers later in the year. This box also has 48GB of ram, and by the sound of things is a bit similar to Christoffer's. Of course this machine/computer is build specifically for doing work in the Digital Darkroom.
I may offer a "write-up" later in the year. Anyway, regarding setting up the hard drives, this applies to both Mac and PC, only on the Mac you do not have much room beyond 4 HDD, or 8 SSD's using special brackets, and you could remove the optical drives and fit more there! :-)
So, if you decide to get a new computer, be it Mac or PC, let us know if we can help you Pimp it up :-)
All the best
Henrik
PS: The Shortcuts on the OSX are shorter and often easier to reach then on windows
PPS: Schewe!!!! though not officially supported
, but it has been done, running OSX on a PC :-) ....Nothing like running OSX with 24 cores at 4+Ghz!!!