My Not-So-Objective Bottom Line
The F3 and the FA are not really competitive cameras. My uses give a slight edge to the F3.
The FA is a small, full-featured compact camera for taking fun pictures. It is probably the most sophisticated manual-focus SLR ever made and lets you do a lot of things that later models do not — like matrix metering and program mode with AI-s lenses. It doesn't need a motor drive, it's light and its dead-battery speed of 1/250 means that you can take pictures on a sunny day, even if the MS76s have given up the ghost. It has a good selection of accessories for general photography.
The F3 is... whatever you make it. I see the MD-4 as an integral part of the camera, one that gives it heft and transparency in shooting. It certainly improves the ergonomics, since the body is tiny and hard to grip without it. The F3 is a great, basic bulletproof camera that can be made to do almost anything. It is a must-have for prolonged, wide-open shooting with fast telephoto lenses, due to the virtues of its viewing system (especially if you have glasses). The downside is that even by mid-1980s standards, the F3 was a relatively primitive camera. But primitive works sometimes...
http://www.dantestella.com/technical/nikonslr/nikonslr.html