Frankly, there aren't too many differences in terms of shooting capability. If you're considering buying one, then you gotta do your own research...
From
skimming the F75 specs on Nikon's site, I gather it has almost all the features I'd want on an AF SLR:
- matrix, centre,
spot metering
- DOF preview
- exposure compensation
- multi exposure
- rear-curtain flash sync
- has an optional remote
- the optional battery grip has a vertical-format shutter release which the F80's doesn't, apparently
The F80 has a few 'bells-&-whistles' which may not be necessary:
- many custom functions, e.g. does the AF-lock/AE-lock lock focus, or exposure, or both? and more
- on/off gridlines: convenient for levelling archit/landscape views
- flash comp, in addition to exp comp: not to over-blast insects...
- can take a simple, cheap cable release (+ or - feature depending on your needs)
Both cameras do
not have mirror lock-up or work with manual lenses though!
But finally what matters is whether you need any of those functions; that depends on your style/subject, so you need to consider the options.