The Blu-Ray in a PS3 instantly makes the PS3 better than the 360 for an entertainment centre. Not to mention that PS3 also has a list of impressive features to make it a very viable entertainment hub. I've had a go with some of the entertainment features the 360 has, and while they are fun, the PS3 is much more full-featured than the 360 in this respect. I'm not bashing the 360, i just think that maybe Ballmer over-played the 360's capabilities in this respect. Also (and this is a massive side-issue) the PS3 looks nicer in terms of an entertainment hub. It's got that nice, sleek, matte black, not very intrusive outer shell that will fit in better aesthetically than the 360 which is white (black for the newest ones). Also, the actual shape of the 360, for me, screams "aggressively styled gamer console". If i was pitching the 360 to my mum as an entertainment hub, she'd take one look at it and say "it looks horrible!". While, with the PS3, she loved the looks instantly.
Still, competition is good for everyone, keep at it MS, let's see what the 360 can be made into.