I like the Canon 40D's colors better. They seem more neutral. The K20d has an less pleasing over-saturated "bright" tone to it (which, I presume, is the default setting to satisfy the American reviewers (Phil, etc.). Strange that the Canon does not do this, though.
The Canon 40D seems to have focused on the text in the background, throwing the camera in the foreground slightly out of focus. The Pentax K20d seems to have chosen the old Pentax camera to focus on (maybe it is biased towards its older brother
), throwing the text slightly out of focus.
In terms of noise the Canon is slightly better in my eyes. The Pentax has more chroma noise. E.g., in areas that are mostly black (like the body of the old Pentax camera), the K20d introduces a few multi-colored speckles at high-ISO. The 40D is nice and black.
In terms of overall noise I'd, again, pick the Canon as the winner by an ever so slight margin. However, if I resample the Pentax image to the smaller resolution of the Canon, the Pentax's noise is far superior. ISO 3200 is practically noise free, if scaled down to 10 megapixels.