As Slow Draw says, apples and oranges are tough to compare. Most diets require both.
Mighty: easy, automatic, very good flavor, very session-based, perfect for more than person, unrestricted draw. Ugly, plastic, pain in the ass to clean. Bit of a weed hog thanks to conduction, not all that portable or stealthy. Amazing vape, but not for all applications.
FF2: easier than FF1, but still manual, requires intervention. Unparalleled flavor, great for small loads and single-use, somewhat restricted draw, extremely conservative, no waste whatsoever. Dead easy to clean, takes 1/10th of the time to maintain over the Mighty. Perhaps the most beautiful and sleek portable on the market. More portable by far than the Mighty. Again, amazing vape, but not for all applications.
Choice between the two? Good luck.
I wouldn't live without either.