A fibreglass enclosure is made by draping a form “the mould” with resin-impregnated strips.
The main advantages of this type of material are its relatively low mass in comparison (1,85 g/cm3), its flexibility in all directions and its linear tear strength.
If your application does not require exceptional mechanical strength, your enclosure made via the sheet plastics bending process will be significantly more economical. As this process does not require any specific mould, high investment costs will be avoided, and modifications can be implemented between each production run.
In some cases, manufacturers offer injected PET housings reinforced with glass fibre particles. This case has the characteristics of a standard plastic case with higher mechanical resistance.
The only criterion in favour of fibreglass enclosures is a much higher mechanical strength than plastic.
Without this need, the plastic solution will be much more effective.