Let me clarify my suggestion: The 360 is a piece of crap for local media streaming, with very limited codec support and poor FF/RW functionality. This improves within Media Center Extender, but then you have the "multiple implementations" problem. The 360 is bloody fantastic as a web video streaming device, offering up the most solid interfaces for the majority of video apps compared to any competing web streaming device.
By comparison, the PS3 makes a pretty good local streaming device, as you've already experienced. It is pretty crap for web streaming though, as the apps tend to be very poorly laid out, crash-prone, and very limited in selection.
If you want access to your local video everywhere, get the PS3. If you instead make the choice that "you know what, I don't need local video in the bedroom, as the web streaming options are vast", then get a 360.
In my house I have a 360, PS3, and HTPC in the living room. If I want local streaming video I use the PS3. If I want web video I use the 360. I never use the HTPC. The hardware is great, but the user experience is crap. Maybe I'll try again with Windows 8. In the bedroom I have a 360 and no other video source. Really, if I'm in the bedroom, then it's fine that all I have access to is the vast Netflix library, the vast Hulu library, the vast Youtube library and my vast 360 game library. Not using local video in the bedroom is no big deal.
I want to again emphasize just how terrible HTPCs are in comparison. The hardware and flexibility is great, but at their absolute best they take far too much effort, and you end up pulling out a mouse and keyboard far too often to configure something. I'm guessing that everyone here saying "Go HTPC!" thinks that a keyboard and mouse is fine in the livingroom and bedroom. These people are doing life wrong. The user experience on either console is far superior. That's saying quite a bit given how very little I think of the usability of Sony's ancient dashboard.