Power

Canon has moved the power switch from the back under the thumbwheel (on the 50D and 5D Mark II) to right up top by the mode dial, similar to consumer models like the T1i. Unlike the Nikon D300s, which changes modes electronically, Canon retains a mode dial, with three custom settings slots. Which design you prefer is very subjective; I happen to like the dial better, especially for accessing custom settings.