The difference lies in the material that the reflective surface is made of. These different materials all have different properties related to durability, strength, and reflectiveness that in turn make them more suitable for one specific application over the other.
Glass is the most reflective material available but also the most fragile.
Polished stainless steel is second in reflectiveness but highest in durability and strength. It is usually more expensive though.
Acrylic and polycarbonate both have comparable reflectiveness and durability levels yet polycarbonate is more resistant to impact and therefore a bit more expensive too.
