Interesting that you chose the higher spec'd Apple then gave it the higher rating. Well...duh! Perhaps the HP IQ800 series with similar size screen and the same 9400M graphics (available with a Blue Ray player, even) would have been a better fit. Or compare the 20" Apple with it's lower resolution, comparable to the HP.
And why is the HP noted to be difficult to move around, but the same comment is not made about the 24" screen Apple?
Since you were demonstrating an array of products, the rating should have reflected price. If one only has $800 to spend, it doesn't make any difference how good the Apple is, you can only compare the Atom machines.
Frankly, these machines serve different purposes. The Atom machines are what netbooks are to the laptop world. They are not intended for the power user, and that should be considered in their rating. My mother would be well served by a simple machine that does email and a few simple tasks well, without taking up much space or cost.
But I have no use for such a basic machine. The HP and Apple are desktop alternatives, and really cannot be directly compared to the Atom machines, because they are not marketed to the same user. But, they do have to compete for my dollars with a full desktop, and they fail miserably, even compared to my current machine with its 8800GTS 320 graphics. I'm looking at upgrading my machine, and I can upgrade my box to I7 920, GTX260, 6GB (and a smattering of other stuff) for about $800 (I roll my own, in an aluminum case that's seen about 3 MBs so far).