Nowadays, with careful shopping, an N90s can generally be gotten for $50-60. I actually paid $31 for one, INCLUDING shipping, in very nice shape on the 'bay a couple of months ago. And the N90s doesn't have a plastic take-up sprocket that's prone to break like the F-100. IMHO, the ONLY significant advantages of the F100 are the ability to work with G-lenses, and the faster motor speeds. I think that the N90s is 85~90% of the camera of an F100 for 25% of the cost.
If you seriously shoot film, you will find the advantages of multiple bodies which can have different stuff in each - fast or slow, color or B&W, etc. For that reason, and given the silly low cost nowadays of these cameras, I would suggest that TWO N90s bodies, or one N90s and one N80 (which can use the G lenses), offers better functionality than just one F100 body.