I think if you want to play online Xbox 360 is better. Xbox live is more popular than PS3 online, because 360 is more affordable and more no. of people have it.
And for PS3 having better graphics than Xbox 360 read a few lines of the article or click on the link to read more
[highlight]
h2Performance/h2
If you pay attention to actual game developers, and not the angry fanboys, you will learn that no, the Playstation 3 doesn’t have “more graphics power” than the 360. The fact is, XBOX 360’s Xenos GPU itself has far more computing power than the RSX GPU
that resides in the PS3. Does this mean the 360 has “better graphics”? I don’t know, that is a subjective matter, beyond the scope of this objective
comparison, and entirely up to you to decide.
[/highlight]
Source: http://www.hardcoreware.net/playstation-3-vs-xbox-360-two-years-later/