Whether your redoing your plumbing or starting from scratch this question is going to come up: "Should I go with copper pipe or PEX pipe?" Vines Plumbing and Water Restoration has broken down the pros and cons of each.
Cost is one of the biggest deciding factors in any decision. The cost of copper pipe is 4-6 times higher than PEX. PEX is flexible which can cut down on the costs of fittings as well as the potential for a leaky connection which could save you a plumbing call and a lot of cash in the future. Copper pipes have a far greater chance of bursting when water freezes in them, but copper will hold up better to overly chlorinated or overly acidic water compared to PEX. PEX can't be used outside in the open like copper pipe can.
If your planning on doing your own plumbing PEX will likely be easier to install yourself. Copper fittings require soldering, plus you may have to flush your system to remove the residual solder and flux when you're done. PEX can have long continuous runs with no need for couplings, and PEX can be bent around corners so there's no need for an elbow fitting.
If your trying to be eco-friendly keep in mind copper is 100% recyclable and PEX is not. However, copper allows for higher flow rates which could lead to you using more water.