Taylors are shipped with Nanoweb strings. I've used both the Polyweb and the Nanoweb strings. There is a definitely difference in feel, look, and tone. I'll describe those differences, but it doesn't mean the strings are actually made this way:
The Polyweb strings seem like they are first wound before being coated. It's as if a nylon stocking were slipped over the entire string. Like I said, I don't know if they are coated this way, but when they've been on my guitars for a while, the coating first starts to pill then it starts to lift off the strings. To me these sound a little more muted than the Nanowebs.
The Nanoweb strings seem like they are coated first then wound. I can feel the individual grooves of the wound strings much more than the Polywebs.
I haven't had the Phosphor Bronze strings long enough to see how they wear. They do feel stiffer and are warmer than the Nanowebs.
Here is a visual graph from Elixir's web page that shows the Polyweb strings are the warmest sounding, the Phosphor Bronze are in the middle, and the Nanoweb strings are the brightest (please note Elixir didn't list them from warmest to brightest though).
Elixir Strings GraphicAnd here's Bob saying why he uses Elixir strings...video comes from Elixir's web site:
Why Bob uses Elixir Strings
