- Bonding and strength
Epoxy is known for its higher overall bonding capabilities
- Resistance to wear
Epoxy is more resistant to wearing, cracking and peeling, and corrosion or damage from chemical or environmental degradation. Polyester is more fragile and useful for temporary fixes, of less-stress use.
Epoxy is generally more expensive than resin, due to its strength and formulation requirements.
- Resistance to moisture
Epoxy is more moisture resistant, and certain formulations can even be applied underwater. Polyester resin has minor resistance to moisture, is considered water-permeable, and can fracture easily.
Polyester is far less pleasant to work with than epoxy. Although it sets up much faster, it has the reputation for stinking badly enough to burn your nose hairs. Make sure to use proper ventilation when applying both epoxies and resins.