I find an advantage is that the consoles are made for gaming, and games are designed for those consoles and their specifications in mind. If I put a Playstation 3, I know any PS3 game that I buy over the next several years will work on it.
Whereas, with PC gaming, it's much more subjective. A game like World of Warcraft or The Sims might work on my laptop, but my laptop might not be powerful enough for a game like Crysis 2 or The Witcher or something like that.
Also the price. Nowadays an xbox will run you maybe $300, a decent gaming PC will be over $1000 with a decent graphics card and ram.
Also, there's availability, more games come out on consoles for the most part, than they do on PC. I also find a lot of games to be easier to play on say, an Xbox or PS3 than on a PC. i.e. I find it easier to control racing games and shooters with a controller over a keyboard and mouse. But that's more of a personal preference than anything.