that is SO controversial, because there is NO true answer. whatever anyone tells you, it just THEIR opinion, in the end. but, let me give you reasons why I think xbox is better:
xbox has hd streaming (essentially the same as ps3s bluray)
xbox has sweet apps such as youtube, love film, netflix bbciplayer itc player etc
xbox has internet explorer
xbox has windows 8
xbox has better online (but you have to pay 30/40£ per year for it - worth it in my opinion)
xbox has famous exclusives such as halo or gears of war
xbox is more popular
xbox controller is more comfortable
can charge and play controller with play and charge kit, so Jakob is talking utter rubbish
battery on xbox controller lasts longer in my opinion, and the "bulky-ness" is what makes it more comfortable (personally). i HATE the ps3 one - its so skinny and i cant grab it properly.
the trigger buttons are more comfortable on the xbox - like a real gun
FYI xbox slim doesnt get red ring anymore
xbox slim has 250gb hard drive
NB: all the the above are my personal opinions!!!!!!!!!!!!!!!!!!!
i own xbox 250gb slim and tried ps3 also