Coco matting is looser than compost and thus retains water better. It also tends to be sterile. I use a lot of Coco/coir for my seedlings as it works well. I can see it working well in a hanging basket as it retains water better than compost but whether it is 'best' I cannot answer.

Whether it's best or not is a personal opinion, but as Kildermorie says it hold water better than compost, so baskets lined with it would not let as much water flow straight through the basket, which is what happens if you use the traditional moss lining, Derek.