I have and use both but my computer of choice is the Mac, hands down.
First, I do not have to worry about all the cables to connect a monitor, speakers, etc, as it is all one unit. I don't have to worry about having access to the CPU, again, it is all one unit - there is no bulky CPU.
I haven't had an issue with finding software. In fact, I can find pretty much identical or the exact same software for my Mac that I have on my PC, with only one or two exceptions. I use mine for word processing, internet, digital photography, making and editing videos, making DVD's, CD's, listening to music, watching TV shows and movies, photo editing, gaming, and the list goes on. I love it! In fact, our family has become a mostly Mac family, although we still have PC's. I bought my iMac about 3 years ago and it is still relevant and still going strong, whereas I burn through PC's in about 12-18 months. (Meaning, the PC is no longer able to support my needs and I buy top of the line PC's.) I am a very heavy user.
That being said, you will spend more money on a Mac. In my opinion, it is well worth it. You may need to replace your software, such as Microsoft Office. You may need to re-learn how to perform some functions, but it is pretty simple to switch. Even my 60-something year old parents were able to switch easily. You may want to upgrade to a wireless keyboard and mouse. These are not cheap.
Did I mention that you don't have the computer virus issues with Macs? And, there are many great online forums (including on Apple.com!) where you can go for help if you should need it. And, all of their applications are set up to run with the same basic commands, so you only have to learn the basics once.
My next computer will be another iMac. But, if this is the route you choose, be prepared to pay for it. And, invest in Apple Care, it is well worth the cost.