No they won't - unless they are sitting next to each other.
Once you put a lens on them, they've got no idea.
When I was with my ex, I could get a new camera and she wouldn't have a clue. Same with lenses.
All she saw was a black thing with a lens on it.
I had a 10D and then bought a 1D MkII and she never knew that I had the 1 Series until about 3 months later when she came into my office and saw the two bodies on the desk.
Yep...the girl who sent me the message about wanting a "big, professional looking camera" has her eyes set on a Nikon D3100 with a kit lens...
Saying that the average person knows the difference between a 5D and a Rebel is like saying the average person knows the difference between a Lamborghini Murcielago and a Gallardo...they both look like fast, expensive cars to them, and that's it.





