I also have an F3. I actually chose it over the 5N. It was not an easy decision and I have had some question about the wisdom of that decision after the purchase, but not based on anything negative that I can point to about the camera.
I chose the F3 because I got a good deal on the camera bundled with the EVF (which I really wanted) and I wanted the built in flash so I had the option of using a flash and EVF at the same time and could play around with bouncing the flash and fill flash. I decided that for my photography level at this time, what I typically do with my pictures (most are viewed on he computer and shared online with only a small portion printed and fewer yet printed in a large format) and what I shoot (usually not things where I would benefit from the faster shooting mode of the 5N), any potential image quality differences would be minor, if noticeable at all and I was better off spending any savings on a lens. Obviously your situation may be different. Freddytto (who was very helpful when I had questions) reached a different conclusion for himself and found enough of a difference between his old 5N and the F3 to ultimately choose a 5r. If you look at some of the pictures he posted when he was trying out the F3, however, I think you will agree that it is more than capable of great images (like all cameras, assuming it is in the right hands).
Not sure if I helped or just added to the confusion