Your decision should be mostly based on your budget and the look you are going after. On a sheer cost and performance basis the good plastic models come out on top. You can replace quite a few plastic showerheads before reaching the price of a good metal showerhead.
is self powered by water and doesn’t need batteries to show off its cool LED feature! Not only do you get the benefit of having lights in your shower, the LED comes with a three year warranty, and a lifetime warranty for the rest of the parts. Upgrade your shower system with an easy to install shower head! Take advantage of the water saving technology of this shower head and save money while being eco-friendly. This shower head features a chrome plated finish, which looks very nice but doesn’t have the heavy weight that real metal shower heads do. This shower head also has luxurious features with five functions– saturating, massage, and bubbling spray, with combinations of saturating/massage spray and saturating/bubbling spray. This showerhead features a three way diverter mount and shower hose as well.
Hmmm, interesting question, we've always had really hard water, and always had that problem with mineral deposits as well. Personally, I prefer the metal shower heads and have never noticed a problem with corrosion when using them. On the other hand though, I've had many flimsy plastic shower heads fall apart from the pressure of the water.
What is the current thinking on plastic vs metal showerheads? The plastic ones look cheap to me. The salesperson says that corrosion is a problem with metal showerheads. He also says that you can't get a fancy spray pattern with a metal showerhead.