the cheap stuff just has polyester fluff inside.
the mil spec stuff has 6 or 7(?) strands inside and each of those is made of 3 threads.
not gonna make any difference if you're gutting it, not much difference if you're using it for short lanyards, zipper pulls, keyfobs or whatever. however if you think you might want the individual strands for lashing or improvising fishing line then it might make a difference.