a feed-forward loop gives you a "faster" responce to the demand because the P-gain has just shot through the roof!!!!
For high bandwidth you want high P-gain, BUT this comes at the price of instability AND steady-state errors
Feed-forward gain use to always be used, but that was EARLY electronics for radio transmitters when the amplification & bandwidth was very low, thus feeding some of the input to the output was required to get and reasonable gain.
With increase gain and bandwidth with increase in tech problems started to occur, until some control person proposed the idea of feedback rather then feed-foward (he got shunned for it)
the point being he was right, feed-back gain allows for a constant gain over a wider freq-range (as opose to open-loop with declines with freq and feed-foward that is !!!)
you really do NOT want to use feed-forard! you want an example of feed-foward? OPAMP with +ve feedback... also known as a comparator with hysteresis, its ONLY usable for the two extremes of the output range NOTHING inbetween.
you want faster responce? look around yr cct, faster OPAMPS (lm7171 has silly speed) reduce RC around the place
Also do you really want "D" gain, they are good in theory and when at Uni they sounded perfect (slow the loop down as it closes to the target) BUT in practice where there is this thing called noise "D" gain gets used in ONLY one or two places, and even then it is a small percentage of the overall gain