In the image you can make out that the two are very similar, but the Mitsubishi HD1000U's blacks are just a little bit darker.
In the image below this is a closeup of a frame with some bright areas. What you see on the two projectors is different, since you are seeing the top right of the Mitsubishi HD1000U, and the top left of the image of the PT-AX100U.
Again, the black levels are virtually identical, with the Mitsubishi being - just the tiniest bit darker. A truly, I repeat, truly, insignificant amount, that the eye would not normally be able to discriminate even side by side, because of the brightness below, on the actual image frame.
So the bottom line, on the darkest scenes, the more expensive Panasonic can deliver blacker blacks, but not on more typical frames where there are some bright to very bright areas.
Please note, that dynamic iris action can often be visible to the eye, in some scenes, such as a fairly dark one where a bright object enters the scene. As soon as it does, the iris has to open and all the objects get a little brighter. (It's sort of like someone is playing with a dimmer on the lights in the room - when the white object enters the image the walls all get slightly lighter). Note: The PT-AX100U did a particularly good job of minimizing the visibility of the iris opening and stopping down, but if you are looking for it, you can spot it - on the right scenes, or on scene changes in some cases. Not a real issue in this case.
The standard DVD image of Gondor, from Lord of the Rings, above, brings out all the detail in the buildings and rocks, and you can even make out some details below the arch on the bottom right, despite, (and I apologize) this image being slightly underexposed.
You'll find this image above (standard DVD) also used on most other reviews published in 2006.
OK, sports fans, your turn. This first image along side, gives you an excellent idea of how the room lighting was when the sports images were photograph.