It would depend on how you're shooting and how the picture is used for.
Let's just compare a simple difference on Nikon.
Let's say they both use a good camera, say a D700 and one uses a 70-700 f2.8 and the other uses a 85 f1.4
Both shoot the same subject at the same distance and same focal length to even things out, but one can only shoot at f2.8 (the zoom) and the other has a option of opening up to f1.4
The bokeh difference would be quite substantial.
Now in the other way of looking at it, if you allow the 70-200 user to back off and shoot at 200mm f2.8, then it'll be a different story.
next up, if there is a difference in bodies, with the same good lens, you'd have a difference in terms of megapixel count, noise control and speed of focusing, etc...