Well, as things move on, technically not a lot. At this point most of what's missing in either platform can be made up for in software, and XB360 isn't dependent on an external machine as seemed more the case at launch. What has struck me is Sony's support of the iTunes format, which is quite a big deal I think. But then PS3 won't support the MS formats. I'd say Sony are in a better position to support alternative formats though, because they don't have a software codec agenda. MS obviously want to promote their own standards. WMV is a given, but are they ever likely to let you watch QuickTime movies?
Also PS3's more open support of peripherals is quite the plus-point I think. How do you read a MemoryStick on XB360? Do they have a MemStick reader peripheral? The included card slots in PS3's Supremo model make it a better device in that respect, and on the cheaper side, in theory I guess you can chuck in any USB card reader.
Isn't that what a reserved SPE is supposed to do? It needn't encode to MPEG2 or VC-1, but could use a proprietary compression that fits neatly into the SPE, and which can be converted for export if wanted. Given DRM, I wouldn't be surprised if that was frowned upon. Recording HD content off TV and being able to rip it and burn it and distribute it, much as we consumers want to do that, is something the content providers want to stop.