What version will have better graphics, PC or Xbox 360?
Both versions use identical art assets, and the shader code for a 3.0 spec PC and the 360 should be the same (though there will be slight differences in how they get compiled). The visual differences should be extremely minor due only to differences in display technology, slightly differing data formats between Xbox and PC, and very slight differences in the path from rendering hardware to display. Basically, attempting to choose one version or the other based on visual differences inherent to the software is relatively futile. Your choice should be based on your relative setups - your PC hardware and monitor and how much importance you place on mods vs. the quality of your television and your preference for playing the game with a console controller.
On loading times
It was a 400% improvement based on what Oblivion's load times were previously, not a 400% improvement over Morrowind. Oblivion's load times should be on par with other 360 games. You want to play a game that uses a ton of data like Oblivion? Then you're going to have to wait while the data gets loaded

That's just how software in general works.
On Oblivion's HDR Implementation
It uses full HDR for 3.0 cards, and image space glow (basically what you refer to as "bloom", with a few tweaks) for 2.0 cards.
You cannot tell from a screenshot what lighting model we're using. By definition, HDR is a dynamic effect (it's the D in the term after all) and obviously that doesn't come across in a screenshot.
Xbox 360 version set to a maximum of 30 FPS?
It's 30 just like every other 360 launch title as far as I know. PGR3, Kameo, Perfect Dark, Madden all run at 30.
Will anti-aliasing be used on 360?
Yeah, we use it.