Honestly neither. A Vista HTPC is really your best option for HD content.
Can play divx along with standard wmv files, plays WMVHD flawlessly.
Upscales lower res divx really well
Great UPNP with Windows Media, along with Media Centre Extender
Ordinary DVD playback, but can play HDDVD with addon
Plays Divx, although a little more fussy
Not too good at upscaling divx
Good UPNP can be a little flakey
Great DVD playback and of course BD.
In the end either will do the job with Tversity. It's still the best way to stream media and if you base PC and network is good enough it can transcode HD content on the fly.
I guess it'll come down to which console you like the most. PS3 is quiet but can't be used with a universal remote. However will work with almost any Bluetooth keyboard/mouse. The 360 uses a standard IR so it'll work fine with an universal remote and has better/more games (I know I wasn't meant to mention that. :