The Chronic will be better all-mountain, wider waist, rocker.
In the Park, the NFX will be stiffer, more responsive, stable on jumps. The Chronic will be playful, buttery, and give you a wider ski for rails.
As far as durability, the Chronics might be better. Not sure how the NFX hold up though, Salomon has had delam problems in the past with the Suspect.
I would mount the NFX center 100%. Personally I would center mount the Chronic as well, but if you feel you will be doing more all-mountain than park, you might consider the recommended mount