I assume you're referring to the Canon 5D mkII and Sony HVR-Z1? If not, ignore the rest of this post.
The Canon is an SLR still camera which happens to produce great video, while the Z1 is an early HDV prosumer video camera.
The Z1 has 3 1/3" interlaced CCD imagers, while the Canon has a large 35mm film-sized progressive CMOS chip. This means that the Canon can give an image with a progressive frame rate and narrow depth-of-field that is very filmlike, while the Z1 will be very video-ish.
The Z1 records to HDV tape, while the 5D records to h.264 files on SD cards. HDV is relatively easy to edit, but the 5D has less compression with a more efficient codec. Both are not exactly ideal.
The Z1 has XLR audio capability, while the 5D requires adapters.
The Canon can only record a 12 minute long take at a time, while the Sony can record longer takes up to the length of the tape.
Very, very different cameras for different uses. What do you need it for?