yeah, i know you can stream video/music to ps3 from your PC, but i think you can do that for the 360 too? browsers better on the 360 from what i've heard, but you have to pay for the privilage. but the linux OS is a brilliant idea for the ps3, although you need to download the iso to your pc first!
if you're in the US, then you can use the ps3 movie store. if you're europian, then you can purchase playTV, for watching/recording at the same time, in upscaled ability. (and watch your movies on the toilet, or with wireless anywhere in the world on a PSP)
hardware is more reliable with the ps3, as the 360 can allegedly scratch your disks, and occasionally, you may get a 360 that'll have the Red Ring of Death! all that means is that a peice of solder comes loose inside the machine, and then you send it back to MS, who will send you a replacement.
360 does have more varied game collection, but the PS3 is starting to catch up.
the fact that you can use the PS3's bluray for video playback in 1080p is a bonus too!!
I think you can do the same sort of thing with the 360 as an all in one centre, other than the bluray player, if you go for the elite version. Both Upscale DVD's.
however, i've bought another PS3 as an all in one media centre for my sitting room, as you are thinking about doing yourself, and i'm more than happy!
tried to make this argument as equal as possible, so no FANBOYS from either console, no getting grumpy please, unless its constructive!!