You'd hardly notice the difference between the two clips. The 5D is a slightly different beast to the 7D. The 5D will give you shallower Depth of Field at the same focal length as on a 7D.
They'll mix fin.e. I'd suggest using the same color profile on both. I rent 7Ds for the 60 fps (slo mo) on 5D music video shoots. I think the 5D is "better" because I like the Full Frame look, but in some ways the 7D is easier to work with because you aren't fighting really shallow DOF as often.
The 5D, from what I've seen, looks fantastic. But. My 7D is the best thing I have ever held in my hands. So...cost-efficient. I've been getting some footage, that, when color corrected, looks like the RED One.