Not to mention that the 5D has established its name in the younger high school/college student crowd.
This is the same thing that happened regarding Nikon's D90. Back when the D90 was super popular, most high school students or college students could name drop the D90. If they heard about any camera, it was most likely the D90.
Now it is the 5D that took that spot. There's a good chance that anybody remotely interested in cameras has heard of the 5D and/or knows about it. Not many of my friends know of the D700/D800, but many of them know about the 5D.
So in terms of name recognition alone, Canon has the upper hand (at least with my experiences).