If you do a side by side comparison of a 5d vs. 7d, you'll notice.......
5d 98% coverage, 7d 100%
5d 3.9 fps max, 7d 8fps high
5d:
35-zone TTL full-aperture metering
Evaluative metering (linkable to any AF point)
Partial metering (approx. 8% of viewfinder at center)
Spot metering (approx. 3.5% of viewfinder at center)
Center-weighted average metering
7d:
63-zone SPC TTL metering with selectable modes
Evaluative metering (linkable to any AF point)
Partial metering (approx. 9.4% of viewfinder at center)
Spot metering (approx. 2.3% of viewfinder at center)
Center-weighted average metering
5d compatible lenses: ef
7d compatible lenses: Canon EF lenses including EF-S lenses (35mm-equivalent focal length is approx. 1.6x the lens focal length)
Other than the above, they both have eye level pentaprisms, same shutter speeds, same metering ranges, and same High-sensitivity, high-resolution, large single-plate CMOS sensor.
So a 7d has more perks, including price, and is slightly more versatile as far as lens choices. The main advantage of the 5d seems to be 21mp.....sooo the question is are 3 more mp worth it to you?