Xbox Live is worth paying for due to the updates and the level of competition on Xbox Live. PS3 does not have any Professional Gaming Ladders anywhere in the world. Anyone who plays competitvely or Semi-Pro plays on Xbox 360. I actually have just sold my PS3 due to clan inactivity, but I will say the few exclusives for PS3 that have released lately ( Killzone2 and Uncharted2 ) were definitely both worth spending the money on. My major pet peeve with the PS3 was the update size and time to download. I had just purchased it and started building my game collection and would get home and have to wait for 20-30 mins before I could play.
Xbox 360 takes not even a minute to download an update for a game. The dashboard for the 360 is more user friendly where as, you don't have to leave the game your currently playing to change system settings. Theres also the " Party Chat " option which lets you voice chat across games instead of having to clumsily text a message out between rounds of a CoD4 game. With the pay to play experience of XBL, you also have the benefit of cheaters being banned from XBL so there isn't hardly any modding, minus your occasional rapid fire controller. When you really think about it though, for roughly $50 - $60 a year XBL doesnt cost a whole lot compared to other online gaming networks ( i.e. World of Warcraft $15, Final Fantasy 11 $15, Dungeons and Dragons MMORPG $20 all each a month ).
In closing I will say this, PS3 is a great ADULT owned BluRay player and gaming console. Graphics are amazingly smooth and crisp for every game out. In turn though, if you want challenging multiplayer and a solid foundation for anyones gaming console collection the 360 is the way to go.