I don't think there's a one-stop page that compares all of them...
Off the top of my head, the FF1 was a LuxIII, twisty, one-off, black-colored anodizing that was made in small quantities. It used optics, which gave it a square beam, and had an angled keyring on its tail, which means it wouldn't stand on its tail. It was a twisty. Quite rare.
The FF2 was more or less the same, but with gunmetal anodizing, produced in larger numbers, the tail was re-designed so it could stand on its tail, and had an option of a resistor-based 2-stage output for its LuxIII. Still used optics, and was a twisty. The FF2 came with an option for an aluminum (vs. copper?) "middle piece" to reduce weight. I got one, and like it a lot, but there's a bit of flicker when trying to enter the "low" stage.
The FF3 is the current model that uses RCR123's ONLY, uses a reflector instead of optics (yay), and uses some fancy circuits to control the output (instead of the resistor). I was away from the forums during this time, so I missed out on this, and don't have much to say about it.
That's just from memory, but if you'd like, you can read up on it here:
This FAQ will get you caught up to the FF2:
https://www.candlepowerforums.com/threads/50547
This page will get you caught up with the FF3:
http://candlepowerforums.com/vb/showthread.php?t=89078