I've owned both in my time, but no longer do - I'm still with my Nikkormats, ELs and FT2s, which have served me well since I bought them new and still do on those rare occasions when I shoot film.
If I had to choose between your two preferred ancients, I would go with the F5 - built like a Sherman tank, can be used as a defense weapon, and seems to always keep on shooting.
The main advantage of the F100, on the other hand, is when it dies (and it will), you can throw it out and buy another.