It depends on the materials, application and function of the system.
Generally coating is an easy way but if you do not form a good and homogeneous film you may not repeat it and you may not use it for longer periods. It has to be compatible with the textile surface. (surface properties, surface energy, adhesion, viscosity, print ability, plasticizer, solvent, mixing, curing and so on)
If you want to incorporate the fibers, you will bend, change the original shape even break the fibers. Depending on the function of the fiber, you may not get satisfied results. Also technology and method is critical in this case. This very important esp. for optical fibers. Also rigidity is another disadvantage for optical and conductive metal fiber incorporation.
If you tell us the application and the materials we can try to help more.
Hi Nantakan, I agree with Dr. Redha's comment. Here I like to add few things:
1. Cost of the fiber formation process is more than the coating process, 2. Coating is effective if the polymer have affinity for the textile materials, which can be improved by adding side chains to the polymers. 3. Coating is a faster and simpler process, but never a durable one(you need to decide on your end use).