This is our standard studio scene comparison shot taken from exactly the same tripod position. Lighting: daylight simulation, >98% CRI. Crops are 100%. Ambient temperature was approximately 22°C (~72°F).
Nikon D40 vs. Canon EOS 350D (Digital Rebel XT)
Nikon D40: Nikkor 50 mm F1.8 lens, Aperture Priority, ISO 200
JPEG Large/Fine, Manual WB, Default Parameters, Self-Timer
Canon EOS 350D: Canon EF 50 mm F1.4 lens, Aperture Priority, ISO 100
JPEG Large/Fine, Manual WB, Default Parameters (Standard PS), Self-Timer
Canon EOS 350D
2,506 KB JPEG (3008 x 2000)
2,882 KB JPEG (3456 x 2304)
While it is possible to pick areas of the image which lend some credence to the EOS 350D's 34% pixel count advantage it's clear that the average observer would not notice these differences and that you would need a very large output size for any of them to become visible.