There are lots of choices when it comes to picking new cables for your bike. Galvanized, stainless, slick, we mainly use the Stainless Steel slick from Jagwire. These guys are pre-stretched and perform very well. Some time ago it became popular to coat the cables with a 'Teflon Coating'. While on the face of it this sounds like a terrific idea, like many things it falls way short in reality. Here's why:
The Teflon is a coating, it is put on the finished cable, it is nice and slick and I'm sure that if you wanted to, you could fry a rasher of bacon on it, all be it a very skinny one, but that coating does not like to be pulled and rubbed through housing and it starts to peel off, now we have strips of coating clogging up inside the housing and binding up the cables.
If someone brings in a bike with shifting problems and it has coated cables we clip them and run slick stainless with new housing. Problem Solved.