I recently saw in the Mishna Brura that wool or linen Tzitzis strings exempt 4 cornered garment regardless of what material it is made of, however strings made from the same material as the garment will permit it as well, but not another garment made from a different material (i.e. Cotton strings will only exempt a Cotton 4 cornered garment not a any other material). That being said, is it better to have cotton strings on a cotton garment or Wool/linen?
Note: This is ignoring the later halacha in the Shulchan Aruch where the MeChaber cautions against using linen tzitzis strings/Garments. It is a question on weather B'mino is more ideal than wool/linen tzitzis- which exempt all 4 cornered garments regardless of their material.