Canon 5D vs 7D

The 5D is better in low light and has slightly better dynamic range. 5D has bigger sensor which gives it a different look, if the look is better or worse is a matter of personal taste.

I wouldn't recommend buying the 7d for shooting video, the video from it is identical to the video from 60D, 600D and 550D which all are much cheaper. All of them also have the ability to shoot in 50 and 60 frames per second which the 5D cannot.

5D has manual audio controls where as the 7D does not, but the 7D has a full HD signal output when recording so you can use an external monitor for pulling focus better. The 7D may have the same sensor as it's cheaper counter-parts but it also has a much more robust weather-proof body same as the 5D.

I prefer the look generated from the APS-C sensors to the 5D personally, but using wide angles on a full frame sensor certainly was it's advantages too.