For what it is, the CX-9 is a good handling car. That said, the AWD is not performance oriented. It is very much biased to the front wheels and it does not do any of the tricks like powering the outside rear wheel during cornering (like Acura and others are starting to do). If you're interested in handling alone, you might benefit from the weight savings if you go with FWD.
Purely from straight line acceleration perspective, (everything else being equal)
< 200hp: FWD wins (thanks to less weight)
200hp to 300hp: FWD or RWD (depending on F=m*a)
300-450hp = RWD wins (thanks to weight shifting)
> 450hp = AWD (more wheels to put horsepower to the ground)
For CX9, the extra weight of 200lbs slows down the acceleration.
Corner handling-wise, many more factors involved. Hard to over-simplify it.
I have FWD 2012 touring and had a chance to drive AWD. AWD feels as a heavier car, accelerates slower. Keep in mind, CX-9 is built as a FWD by its weight distribution, opposite to some other AWD cars like BMWs, some Jeeps, Mercedeses.