Well, everything has been said, but I once had both and prefer the F100, why? Well, the F5 it's just a brick, too heavy IMHO and besides 100% viewfinder, removable prisms and some other bells & whistles, the "F5 Lite" share many of the features of the bigger sister.
Both wonderful instruments, but to me, the F100 is more than enough for almost everything.
Dear Mr know-it-all,
As Jorge's signature line said "If you buy a piano, you own a piano. If you buy a camera you're a photographer."
You forgot F100's!
I'd be willing to rattle can your F5 silver, for a price. I promise to use only the finest Rustoleum has to offer. No warranty on further operation though.
I shoot F5s on a regular basis. The main weakness of the F5 imo compared to modern pro cameras is the AF. It's fast, sure, and 12 years ago was tops, but by todays standards it's dated. Mostly b/c there's only 5 points and they're in a narrow spread. For this reason I usually have the F5s set to manual focus. (This same criticism goes for the F100).
They weren't on your list, but my favorite Nikon bodies are the F3hp and the F6. My F3s see more use than any of my other gear.
The F3 is a fine camera but I much prefer the F100 to it. The F3's major drawback for me is its lack of a spot meter as well as its less than stellar performance with flash (slow flash sync).
Concerning the F5 or F100, I own both and generally prefer using the F100 for general purpose, carry around shooting. I remove the battery pack and it makes for a lightweight and unobtrusive package; love the F100 with a 50mm lens. The F5 I keep loaded with Velvia and mainly just use it on a tripod.
Interestingly, Andre has said almost exactly what a local pro wedding photog said to me recently. She found the F5 very heavy and slightly intimidating for both formal and informal pics. When that was combined with the extra cost of the F5 to give her additional functions that she didn't need then it was an easy decision to go with the F100.
If only the F5 feels right and not getting one were to leave the OP with "an itch that couldn't be scratched" then the decision is equally clear but in that case the question wouldn't have been posed to the APUG community.
The best advice is try before you buy. Borrow both cameras and use them in typical shoots over several days before a final decision. Easier said than done. I wonder which, if any, dealers would allow you to "pay" for the more expensive of the two cameras and hold your money in a kind of escrow account until you had decided and then return to you the difference should you go with the cheaper option.
Of course you'd have to be prepared to buy one from that dealer at the end and risk costs if the camera was damaged in any way. I suspect that these days that kind of "gentleman's agreement where my word is my bond" is getting increasingly difficult to find in a world that glorifies the "winner by any means - fair or foul" and despises the loser as a sucker who deserves all he gets.