I should know since I've done both lol......but I don't know exactly. I'd say the main difference is the intensity phase that DF has. SF (from what I know) is repeating a series of linear progressions based on a 5x5. DF uses a linear progression based on the 5x5 in a much shorter volume phase followed by an intensity phase, then repeated.
I went out on a limb for this one since nobody else posted