Now that the major carpet mills have begun manufacturing more carpet
using polyester fiber, the old addage that nylon is better than
polyester has been debunked.

First, fiber is only one part of the carpet equation and should hold as
much of your attention as the other factors.  The other factors being
the overall construction (texture, loop, frieze, etc.), the density (a
formula of weight and height of the fiber), and warranties.  Density
will vary with your construction and shouldn't be used to compare
carpets unless they are of the same construction.  A frieze is built to
be more loose than a texture on purpose, and so the two types will
naturally have different densities.  You can, however, compare two
friezes, or two textures by using their density.

Second, polyester is a great fiber.  Today, a lot of carpet using
polyester is engineered as "Continuous Filament," so that shedding and
piling is eliminated.  It cleans extremely well, AND IF COMBINED WITH
THE RIGHT DENSITY, it wears extremely well.

Third,  it is also priced better than nylon, mostly because most of it
comes from recycled pop bottles; consequently making it a "Green"
product.  The latest Smartstrand from Mohawk, a cousin of polyester
will soon be made from corn.

The main point here is simple:  Don't buy everything the carpet
salesperson is telling you.  Look at the big picture and make your
purchase accordingly.  If in doubt, ask me.