Fi Q = bottom heavy/boomy bass, can be EQ'd out, but you lose some output. Rolls off pretty quickly around 50Hz.
HDC = tight punchy bass, not bottom heavy but will play low no problem, plays up quite high with authority.
I've been running both of those subs for several years in various boxes, power levels, and vehicles.
Really depends upon your choice of music and what you consider to be SQ. I listen a lot of diff music and that's how each sub sounds to me...