If you build your own PC, you can get a computer that is almost half the cost for the exact equivalent computer in Mac form. The architecture for the components in a Mac are of a different quality than you can find for PC, and they happen to be of high quality as well (Mac fans are always quick to mention this); but still, without getting into the details, if you know what you are doing or if you get someone with expertise to help you can get far more value from a PC than a Mac for less money, far more. And over the years as you upgrade components on your PC, you will save even more than a Mac user.
Some software programs are proprietary for Mac, so that may factor in as well. It used to be that the DAW my friend wanted to use for making music was only available on Mac, for instance. So there could be issues like that to consider. But it sounds like you just want a computer for basic needs, so this probably isn't a relevant factor for you.
I have a laptop and a desktop right now. My desktop is a gaming rig, primarily. I would say it's top tier overall but not quite bleeding edge. I'll spare you the details on the specifications. It's getting increasingly harder to justify from the point of view that I don't really game so much anymore (and I never really played too much really, just a few games I couldn't pass by every year or so). Even if I quit gaming soon, I would still build my own PC as opposed to buy a Mac, on general principle.
What kind of things do you need to store on your computer? This will determine what kind of hard drive you need. Factors like external hard drives/flash drives (whatever you might already have) contribute too. You might be able to spare yourself some expenses if you don't need a lot of hard drive space. I would say also you shouldn't skimp on the RAM. That effects the performance of the computer dramatically, even if you are using the computer for more or less basic stuff. IF you build a computer, the most important thing to remember are 'bottlenecks'. This basically means that your computer is only as good, efficient or fast as the weakest component of your computer. Think of it like a four lane highway being reduced to one lane because of an accident or construction or something. You have all these cars (potential) behind the accident and reduced lanes, but since there is only one lane to pass through, the cars can only get by one at a time. In computer terms, you might buy a bad ass graphics card, but if the motherboard or CPU is inferior and can't handle it, then the graphics card's full performance potential will be wasted. In such an arrangement you might have gotten a graphics card that was half the cost of the bad ass one and received the same exact performance, all because of the bottleneck issue. This mistake is made all the time by gaming people. Just remember, if you build it, your computer is only as good as the weakest part of it. THIS IS ALSO a way to judge the quality of packaged computers: compare the different components and figure out where the bottlenecks are. Sometimes superficially a computer or laptop sounds like a great deal, because it is cheap because you get for example lots of CPU...but when you look closer you find where they cut cost on the computer to sell it cheap, you find a massive bottleneck, etc. and you discover that sometimes the more expensive laptop or computer is of greater value. Sometimes the real deal is the more expensive computer, believe it or not.
OS...lol I miss Windows 98 and 2000 lol. I use Windows 7 now. My complaints about OS by Windows are not relevant for a casual computer user. In fact, I think the casual computer user benefits from the changes over the years of Windows. The evolution of Windows has simplified the experience and interface for casual people but have made it much more difficult for competent users to get deeper in the OS and customize the experience. It sounds like you would be fine with what is available. I like Windows 7 well enough, this one frustrating aspect aside.