My family owns a Wii, and I personally own a PC. With a gaming PC, you really do have a significant edge over the consoles. Controls are entirely up to you, upgrading is easy and efficient, graphics are always better, and you have access to so much customization in terms of modding, whether it be good or bad, settings in certain games, and once again, controls.
Not only on the gaming side, but owning a PC really is cool. I built mine myself, and its great to know exactly what every component does and how to fix it. I've never had virus issues with my PC, aside from things I knew I was getting myself into. If you can recognize bad sites for what they are, viruses are a non-issue.
I also own a DSi and 3DS.
If I had to choose between a PS3 or Xbox, I would go with the Xbox hands-down. While it's sad, Xbox does get special treatment by developers. It also has a superior online service (from my limited experience) and a broader player-base. I also prefer it's controller and simply LOVE the Halo games. I wish they were still on the PC.
Anyway, that's my two cents.