fibred core copper wire vs normal copper stranded wire: is there a difference?

hey guys, quick question.

i got around to doing the removeable cable mod on my m50's, went ok for a first time diy.

anyways, problem is, the wires running from the circuit board to the female jack i added for the mod were weakened and i had to replace one of the original wires with a random copper wire i found lying around which was about the same thickness, just the sleeving was a bit thicker.

tbh the replacement wire i found to be MUCH easier to solder, both on the circuit board and onto the female jack, so im wondering if there is any advantage to using the wire with the white fibres inside.

apparently you burn off the fibres then solder the copper wires onto the board?

if so, there would be only around 4 or so extremely thin (and weak) wires soldered onto the board, which broke off with a quick tug.

it's probably just because im new to this, but i wasted about 4 plugs trying to solder the fibred wire, whilst after i switched to the other wire i did it in one go.

so, is there any reason for the fibres wrapped inside the wires? and is there any advantage for using these wires as opposed to ordinary stranded copper wire?

thanks in advance

EDIT: pics

the one on the left is the one i replced the one on the right with; the one on the right has the fibres.

in that case i'll be replacing the fibred wires inside the cans with ordinary copper wire..

i'm under the assumption that there wont be any quality loss though.

ill probably have to hot glue the chassis so it wont wiggle around and possibly damage the solder connections.

on another note, tips for soldering the fibred wire?

i gotta redo my mini to mini line out cable because a dodgey connection broke off =/