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).
Sony DSLR-A900 vs Canon EOS-1Ds Mark III
Sony DSLR-A900: Sony 85 mm F1.4 ZA Planar lens, Aperture Priority, ISO 200
Manual WB, Default Parameters (Standard), Self-Timer
Canon EOS-1Ds Mark III: Canon EF 85mm f1.8 USM lens, Aperture Priority, ISO 100 (default base) JPEG Large/Fine, Manual WB, Default Parameters (Standard), Self-Timer
Canon EOS-1Ds Mark III
6.1 MB JPEG (6048 x 4032)
5.3 MB JPEG (5616 x 3744)
Although there's a significant difference in price (the EOS-1Ds Mark III is, after all, a professional camera), this is as near to a 'level playing field' comparison as we're yet able to show (until Canon ships a production quality EOS 5D Mark II). The resolution difference is marginal (around 10% more pixels in each direction), and you can see this translates to a very similar level of detail being captured, though again you can see how much sharper the Canon JPEG is - both in terms of edge contrast (per pixel sharpness) and in terms of the level of software sharpening applied. That all said, the differences aren't huge (and are mostly a reflection of Canon's superior JPEG processing) and next to a camera costing more than twice as much the Alpha 900 stands up remarkably well.