It might not be as simple of a question as simply which operating system to run. If you are thinking of switching there are several things you might want to consider. Mac generally goes for a higher end system. Most people then compare their "expensive" Mac with a cheap PC, but that really isn't a good comparison, in my opinion. If you really want a higher end PC you will pay about the same amount of money as for the Mac. But with a Mac you have to be willing to spend more money on the hardware. Although you will spend less on the operating system itself. Upgrading from Mac OS X v10.5 to v10.6 was only $29 while upgrading to Windows 7 will cost you more, and depending on which version you get it can be a lot more.

But the cost of the hardware and operating system is not the only cost you will incur. If you own and want to continue to use the old software you are used to then you will have to buy all your applications again. Microsoft Office for Mac retails for $400, but you can get it cheaper if you look around. But that's just the beginning. If you own lots of software you could easily spend more replacing it than you spent on the Mac itself. And then there's the problem of software that you may have owned but that does not have a Mac version at all, like a lot of games. If you are a big gamer then you might find switching to a Mac a frustrating experience.

However, there is one way around all the software headaches and that is to install Windows onto your Mac. Now if all you want is to run Windows on a Mac then I would not really recommend it, but I have heard reports that the fastest computer to run Windows on is a Mac. You can either use Boot Camp from Apple which is free and it lets you dual boot into Windows or Mac OS X. But dual booting is kind of a pain because it means that you have to shut down the computer every time you want to switch operating systems. The nice thing about dual booting is that you get to use all the memory installed on your computer. Windows in Boot Camp runs very fast and I have no complaints. You could also install Windows inside your OS X by using Parallels, VMware or VirtualBox. I use VirtualBox because it's free. The good thing is that you have access to both operating systems at the same time, but the bad thing is that you have to split up your memory and now my 4 GB of memory is only 2 GB for my OS X and 2 GB for Windows. So both operating systems run a slower.

Another consideration is going through the learning curve of adapting to a new operating system. It can be frustrating, but it just takes some time. I find that there are some things that I think Windows does better and other things that Mac does better. I like both operating systems for different reasons.

With a Mac you will definitely have a lot less problems with viruses and malware, but Macs are not immune and there's always the possibility that things could get worse. With both operating systems you need to keep it updated and run good virus software. Networking Macs together is pretty easy and Windows 7 makes it pretty easy to put together a home network if all your computer are running Windows 7. But making Macs and Windows computers play together can take some work.

Most of my experience in computer repair has been with PCs, but I run mostly Macs at home so I'm very comfortable with both systems. If you want to switch to a Mac I would suggest you start out with a Mac Mini or a MacBook if you need portability. The thing I don't like about them is that you can't do much expanding. With a nice PC tower you can upgrade to the newest video card, add other expansion items, or add lots of hard drives, but with a Mini, an iMac, or any laptop (not just a MacBook) you will not be able to play around with it as much. All you can really do is upgrade the hard drive and RAM. But most people don't mess with their computers as much as I do, so you would probably be fine. The only Mac that has this kind of expansion capability is the Mac Pro, but then you will have to spend a lot of money.

Apple, of course, is ready to help you make the switch at http://www.apple.com/getamac/
You can also get lots of information at Switch To A Mac http://www.switchtoamac.com/
And Mahalo has a nice page on the mechanics of actually making the switch:
http://www.mahalo.com/how-to-convert-from-pc-to-mac