Many use one of the other, for some plumbers it became a personal preference, because it's cheap, easy to work with and it increases production time.

If get to "nitty gritty" Copper pipes are very durable when it comes to a long term but with non acidic systems. It is also bacteria and fire resistant, not to mention earthquake tolerant. and also as a surprize to many copper can be incredibly flexible and bent around joints.

The downside to copper, not sure how true this is but some people claim they get metallic tasting water ( I never heard anyone complain, but you hear about it in some articles) Also if water has high acidic content, pinholes can form in the pipe and cause a leak. As I said before installation is something not many can do and it involves more labor and you more or less you need professional plumber to do it unless you familiar with soldering and know certain tricks of the trade to make copper reairs or modifications and of course is more expensive than plastic piping.

As the plastic goes and since it hit the market there been many positive things about CPVC pipe. Plastic is resistant to corrosion and abrasion, it absorbs the sound much better, and pretty much anyone can install it or make a repair with common knowledge and as the cost goes is much less expensive in comparison to copper.

Now again as the talk goes in some articles I read some people complain that they get a plastic taste in the water (I never heard that from any customers). The pipe is more fragile in comparison to copper if not handled properly it can crack or break. When working with plastic piping you have to have a well ventilated area and I heard that the CPVC itself can be prone to a bacteria growth on the inside in some situations.

I'm sure some have more add to that, but on the general note, both Copper and CPVC both approved materials to deliver water into the home and both materials are being widely used in the construction industry.

Everything else is pretty much are the cost concerns when it comes to choose, for some it's a preference, for some it's health concerns and other than that they pretty much perform the same.

Good luck