*Take a hold of his Ban Hammer from a past life.*
PS3 - Free to play online, can pay extra for DLCs. Also, new this year, you may upgrade your account to PSPremium. For a low monthly fee, you get a whole bunch of free DLC's, free PS1 and Minis, money off all DLCs for all games and 'Rent-a-films'. What lets it down, it has a crappy social feel to it. The only social feel you will ever get with PS3/PSN is PSHome. Playstation Home, as we all know, is the most boring thing to have ever existed. Some may disagree though.
Though, as I have said, PS3/PSN does have A LOT to offer the computer game freakazoids out there. It does have LoveFilm on it, on which, if you have an account with them, you can watch a choice of thousands of titles whenever you want. With no limit. You can also, if you don't find the film you are looking for on LoveFilm, rent a film from the Playstation Store for a low fee, or just buy it outright.
The Playstation Store is extremely easy to navigate, a lot easier than XBOX 360 store. Also, there are no "Playstation Credits" or "PSPoints". It is plain and simply, "£50.00" Where as XBOX 360 is £5 for 800 XBOX Credits or whatever. Brilliant!
I prefer the Playstation because of the freedom of it. "Yes, you can play online with your friends, chat, socialize (To a crappy extent), do whatever you want. For free. But, if you choose, you always have the option to pay this fee to gain extra content excetera." Where as XBOX is more like "Yes you can go online and play and do all of this (Quite frankly,) amazing stuff, but you have to, yes have to, pay us to do so." Yes, in my eyes it's worth the amount of money but I don't like to be forced to pay them money just so I can play a bit CoD with my friends. PS lets you do it for free.
But yeah, in summary:
XBOX Pwns. I mean, really pwns. But you have to pay for it, which is fine. BUT. PS3/PSN is just as great in all these other fields and is free, that there really is no competition for me.
Playstation all the way people.