I have always had a PC, so I can't speak for Mac, but it seems that if you are a Mac fan boy, you usually stay with it. But I don't know anyone who owns a Mac that had previously owned a PC. I am working now on a five year old PC, we usually keep them about 5 to 6 years, but this one will likely stay around much longer. We did once get a virus, but that was my teen son downloading 'free music' and when we took it to get it fixed the first thing the guy said was, 'does anyone download limewire?' That was on the last computer. The fact that they update doesn't bother me, it means they are constantly improving the software.
With a kid in the house, the choice was determined for us by the ability to play games and my husband wanted good sound, and the fact that we can upgrade our video card, audio card and memory. And my husband is not versed in how to do this, but he was able to figure out easily. So a big advantage was the ability to give ourselves a better computer without investing in a whole new system.
OK, I'll say it, I love my PC.