It is more beneficial to use a fiber core than a metal core.
Chemically bonds with teeth well
Although a metal core bonds with teeth, the core, adhesive, and teeth are not completely unified. They are stuck together only by an adhesive that flows into the small grooves of the core and teeth. (Mechanical bond)
If the adhesive leaks out, there would be a space between the core and teeth. It will cause a cavity, and even a tooth crack.
A fiber core behaves similarly to the teeth. Because of that, the fiber resin core, adhesive, and teeth are more likely to be unified. (Chemical bond)
Unlikely to cause a cracked root
A metal core separated from the adhesive and wedging the root often cracks the root. A fiber resin core, however, is unlikely to have the same problem because it can be united with a root.
A metal core is corrodible because it contains a silver alloy. On the other hand, a fiber resin core is solely made of fiber resin, which will not decompose.
Do not produce a silver ion
Unlike a metal core, a fiber resin core does not produce a silver ion, which causes a discoloration of the roots.
Similar elasticity as teeth
Metal corefs inflexibility can cause a tooth to crack. Because a fiber resin core is as elastic as teeth, the tooth is unlikely to crack.