My opinion is only for gaming purposes.. since we buy it to play games... n not its side functions

In term of gaming titles and performance both are more or less identical... before PS3 n XBox came... games titles are mostly stick to their main console maker only...
like if u want to play Sonic u hv to buy Sega, Want to play mario hv to buy Nintendo, Want to Play SNK games must hv Neo Geo...

Now... times hv change... most titles hv gone multiplatform especially for PC,Xbox n PS3... leaving Wii which still cater for their own gaming titles mostly... 
Only some titles are exclusive to some console... like GOD,uNCHARTED n etc for sony's player... n some Microsoft games only for Xbox eg: Mass Effect,Halo,Doa4 n etc...
With FF13 previously was exclusive for PS3 now has jump for multiplatform... n we are seeing MGS series going to Xbox soon...

Interm of built quality, xbox seem a little bit low quality since its noisier and the console face plate breaks easily, while ps3 hv a low noise and steady built casing... visual/Graphic quality are marginal differnce... while some games look better on PS3 like FF13 which was always the game with Sony.. but other titles are mostly identical.. Loading times the Xbox is far more superior... The PS3 load time i longer and the slim ones loads longer than the fat ones.. thats y ps3 games are recomended to install on Hdd to reduce load time...

controller wise.. Xbox design was identical to the Dreamcast and it has a more sturdy grip for players compared to sony's dual shock whisch is a bit too small n flimsy to some adult hands..

so.. if you are a hard core gamer.. u'll find a console that satisfy the game titles for u not what it looks good on paper... usually non bias true hardcore gamer will buy both to satisfy the exclusive titles...