Well, X-Box Live had a year head-start in the online gaming market, so of course it's ahead of the pack. But that doesn't mean the PSNetwork isn't inferior. Live's interface is very user-friendly; it has Facebook, Netflix, the Game Library is easy to navigate, there's really no issues. A Gold Membership will cost you about $50-$60 which lasts for a year (if I recall).
The PSN is very streamlined, as well. If you've ever used a PSP then you'll be familiar with the setup. There's a game section & a movie section, the menus are also easy to navigate. The best draw is that it's FREE, and it has it's own internet browser, which the 360 lacks. There's an optional service called PlayStation Plus, subscription is $49.99 for a year or you can pay less for just a few months. The package includes exclusive demos, content, avatars, etc.
So it's really your call. Both consoles have downloadable SotN, but as for exclusives, ps3 has Chronicles & 360 has Harmony of Despair. The new 360 slim is Kinect-ready, while new ps3 slims come packaged with the Move peripheral & Eye Camera.
Remember how everyone was saying Bayonetta looked better on the 360 than the ps3? That's because 360 was the lead platform. It remains to be seen if that'll be the case with LoS, but I don't wanna take any chances. There's also the issue of installing a portion of game data, which may or may not become a nuisance with future games you may purchase. I'll get the European Limited Edition for 360 though, just for shits 'n giggles (: