Surely the fact that the 450D is 14bits (16384 different tones) and the other two are 8bits (256 tones) is one of the main benfits to the 450D?

The 40D is already producing 14-bit images. The 400D (and most if not all of the previous EOS digitals) are 12-bit. In both cases, if you capture RAW files you get the full bit-depth of the cameras. The loss only comes when you convert to JPEG, which is limited to 8-bit images.

This applies to the 450D too - JPEG images are still only 8-bit output.

400d doesn't have spot metering.

The specs for the viewfinder size etc. is missing. This is quite important!

Storage types: Microdrive should be under the 400D column and not the 450D.
Metering: 400D has Evaluative, not "Matrix" (a Nikon term), and does not have Spot. All 3 have Partial (ie. "large spot") metering.
Exposure Compensation: The info under the 400D and 450D is incorrect. All three cameras are the same, -2EV to 2EV with 1/2 or 1/3 EV steps.
White Balance: This section is a mess. The same setting should be on the same line for each camera so that it can be easily determined where the differences are. All 3 cameras have the presets for AUTO, Daylight, Shade, Cloudy, Tungsten, White Fluorescent, and Flash. "Incandescent" under the 400D should be Tungsten. All 3 can set Custom WB, and all 3 allow WB Shift and Bracketing. The 40D allows directly setting the Kelvin color temperature, the 450D does not.
File Format: "Li-Ion" under the 400D should be corrected to "RAW-JPEG" The 40D can also save sRAW-JPEG.
Energy: Yes, all 3 use a rechargeable Li-Ion battery, but they are not the same. The 400D and 450D use a smaller-sized, lower capacity battery than the 40D.