The PS3's only definitive advantage is blu-ray for movies. It does nothing for games (in fact, the 360's games still use DVD, and almost all of them still fit on a single disc...)
Graphics-wise the PS3 and 360 are about equal. One has better textures, the other has better draw-in depth. Honestly, it's like arguing that 6 eggs is better than half a dozen eggs.
Both now support wifi. The 360 supports 802.11n, but honestly no one has an internet connection that needs that much speed.
The PS3's online service is entirely free whereas the 360 charges you for online play. Honestly, the 360's online service - even though it costs money - is way better than the PS3's. The 360's online integration is a lot smoother and their marketplace is actually organized in a logical manner.
Game-wise, they're both about the same. If you have to choose one, it's going to come down to deciding between God of War, or Gears Of War. Halo or Resistance. Blue Dragon or Valkryia. Etc. Both have good exclusives so again, it's like the egg analogy above.
That said I prefer the 360, mainly for its better controller, smoother download functions, not requiring massive system updates (which take an hour to perform!) on a weekly basis, and not having executives who get excited about utterly stupid things like Home, PSN+, or try to tell us that REMOVING a feature from the console is actually a positive thing. I was a big fan of the PS2 back in the day but Sony has seriously turned me off with their idiocy this generation. They're going to have to work hard if they want me to buy a PS4 down the road.