On our remodel I told our builder I wanted copper on all drinking water sources. I rationalized that I spend enough time in places where I can't drink the water and I wasn't doing that in my own house. We are using PEX for the baseboard heat, PVC for waste lines, and copper for all supply. I know that PEX has its benefits but it hasn't been around long enough that I'm drinking from it (even though I drank from a green garden hose as a kid, I know it's somewhat irrational but it's my money). I don't think your choice will affect resale UNLESS someone finds out that it does leach chemicals and then it will be like Chinese drywall and lead paint - a big deal for some people but not all.

I do not see a reason for not using pex. Are you replacing the whole house? just in the basement? just in a remodelled area?

"certainly for any exterior wall applications (in northern climates). Even though it is better to try and use interior walls, that is not always possible with todays open concept floorplan. With pex you no longer have to worry about freezing pipes that crack." WRONG- While it is true that the PEX tubing will tolerate freezing it also must be understood that when a fixture is installed in an outside wall the PEX fixture stubout is also in that outside wall, and if freezing occurs it can and generally will occur first at the fitting. If freezing occurs in the fitting it will expand the fitting wall and the PEX crimp ring so that when the line thaws and everythig returns to normal size the expanded crimp ring no longer has the correct tension and the line is likely to blow off, not to mention that the end use fitting is copper and it is subject to splitting in the same manner as copper pipe. quote "It is nice when you have a manifold in the basement that equalizes pressure." WRONG- a manifold does not equalize pressure. Pressure changes are a result of vertical static head & friction head in the pipe runs. If the lines are sized correctly their is no more pressure losses in a main & branch system then there are in a home run manifold system. Quote;"allows for individual shutoff valves" Per code, all fixtures with the exception of showers and tubs are required to have individual shutoffs and when servicing a faucett on a second floor I find it much more convenient to reach under the sink and turn the angle stop off instead of running down two flights of stairs and locating the manifold to turn the water off. (Perhaps that is why most local codes still require the angle stops even though you have a manifold system). Quote;" It's also much cheaper" When you factor in the cost of the manifolds & end use stub outs plus the amount of tubing required to construct a manifold system in the end the material cost will work out nearly the same if not more expensive. Quote:" and much faster to install" Here again, this is wrong. While it is certainly easier to fish PEX tubing than to run rigid copper to install PEX per complete code, ASTM & manufacturers specifications it reqiires MUCH MORE attention to detail, but then I doubt if one in fifty PEX installations are really up to spec. The bottom line, if you install PEX in a standard main & branch configuration there is a substantial savings in material costs however if you install a PEX manifold system most plumbers will quote the same price as copper. On the other hand, there is nothing that would prevent you from installing a manifold system with copper, in fact, I once worked on a Jail where they did just that. They installed a manifold in a utility closet in the hall way and a separate copper line to every shower, WC & Lav so if a prisoner should happen to tear something off the wall the guards could quickly turn that fixture off without interrupting water service to the other fixtures on the floor.

Pex has a slightly smaller diameter than copper, which is why there is this requirement. The valves are designed so that at maximum pressure, all of the water will flow to the tub spout. If pex is used, then it's possible that there will be slightly more pressure than the pex will be able to handle and that extra pressure could result in the extra water getting diverted up to the shower head. So the shower head may drip while you are filling the tub. That's the ramifications of your installation. It may not be an issue in your particular case since your specific pressure may not cause this effect, but it's in the instructions because it could possibly happen.