The fact that the chlorination make it more rigid is the main difference btw CPVC and PVC (PolyVinyl Chloride). Actually, this let CPVC to be used on higher temperature, while too cold of a temperature is not good for it due to higher brittleness. This is why some building code only allow PVC (white) pipe to be used in outdoor plumbing for cold water, while CPVC (tan) is coded for hotwater and coldwater for indoor.
As far as reefkeeping is concerned, there is no difference in application.
