Quick example of similar shots with the Canon C300 and FS100, C long and CPF-LOG them Color Corrected and a some light Grading.
my point is: is difficult for me to tell which is which.
Build Quality of the C300 is outstanding and ND wheel is Great, You can feel it worth that much. But at the end of the day what is important (at least for me) is bang for the bucks. For the price of one C300 you can buy 3x Fs100.