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).
Canon EOS 1000D (Rebel XS) vs. EOS 450D(Rebel XSi)
Canon EOS 450D: Canon EF 50 mm F1.4 lens, Aperture Priority, ISO 100
JPEG Large/Fine, Manual WB, Default Parameters (Standard), Self-Timer (with MLU)
Canon EOS 400D: Canon EF 50 mm F1.4 lens, Aperture Priority, ISO 100
JPEG Large/Fine, Manual WB, Default Parameters (Standard PS), Self-Timer (+MLU)
Canon EOS 1000D
Canon EOS 450D
3.1 MB JPEG (3888 x 2592)
3.7MB JPEG (4272 x 2848)
You don't really need to be told that these cameras come from the same manufacturer - the color response is identical, as is the level of applied sharpening. The results aren't to everybody's tastes but, particularly for entry-level cameras, make a generally good balance between being bright and sharp without being day-glo or over-sharpened. These aren't JPEGs that will need a lot of work conducted out-of-camera. The difference in detail levels is incredibly slight, with the 450D making a slightly better attempt to resolve the fine horizontal lines on the middle gold medal.