I did a practical comparison between the Canon 550D and the Panasonic DMC-GH2. I took along five prime lenses and a tripod and set up both cameras with comparable settings, composition. Alternated camera's with the same lens. Everything was shot in 720p because for all practical purposes that's what I use most. Canon was set to ISO 100 and the Panasonic to 160. Mounted with the Carl Zeiss 25mm and 20mm f4 I upped both to ISO 200. Both were wide open, white balance was set to 6000K. Shutter at 50. Canon sat higher on the tripod because of a batterygrip, therefore a somewhat different perspective which is not solely due to difference in 'cropfactor'.(Canon 1.6 vs Panasonic 2.1)
Canon 550D/T2i & Panasonic DMC-GH2 comparison from Filmersblog on Vimeo.