I have the N90s and they are beans to buy, I think the F100 has kept much more of its value, it much more like the modern DSLRs than the N90s is. I don't have the F100 but I do have the F80 and I can imagine the F100 would have much better ergonomics, and I assume it's quieter, the F80 is really quiet.

Their was a rumour at one point that as film camera declined Nikon were going to replace the F100 and F80 with a camera priced between them, I don't know if that was true.