I prefer die-drawn un-coated stainless cables in PTFE-lined housings. There is little if any difference in frictional coefficient between PTFE on steel and PTFE on PTFE, and I have found that the coated cables are difficult to clamp effectively and are prone to the coating peeling.
My understanding is that "stretching" is more of the cables bedding in to the housings than of the metal actually elongating. This even occurs when just replacing the inners; they have to wear their own groove into the housing.