Pros: Better games from all sorts of sources, whether it's Total War, Europa Universalis, or indie games like Mount&Blade. The entire open-source game community on Sourceforge. Better hardware---compare Oblivion on a high-end PC (especially with Qarl's Texture Pack installed) vs. Oblivion on the 360 or PS3.
Cons: A ***** to get working properly, full of frustrated Googling when a game won't work well with your specific rig's configuration. DRM nightmares. Console 'tards ruining the PC gamer experience by getting all the attention on multi-platform games that get dumbed down because they're not smart enough to handle the games the PC master race plays (for those whose sarcasm filter is broken, this is sarcasm, Yahtzee style.)
Overall, though, of my top 20 games of all-time, every single one is a PC game (some are multiplatform but in every case the PC version is by far the best version.) Final Fantasy VI ranks 21st.