Bascially, if you want to mostly use autofocus, you would likely be much happier with an F5. If you would prefer using manual focus, or using older lenses, then the F4 will allow matrix metering with non-chip Nikon lenses; something not possible with the F5.
I picked up an F4S from KEh recently, in BGN condition. I was surprised at how nice the condition of this body was when it arrived. I did add the Dk-2 eyepiece, and later on I got a J screen, since I only use manual focus lenses. I found the prices better at KEH than EBAY.
A G Studio