There are two main types of plastics, thermosets and thermoplastics. Both have advantages is specific situations, but thermoplastics have some distinct advantages over thermosets.
One of the advantages of thermoplastics is that the molding can be carried out non isothermally. This means that you can introduce the hot melt into a cold mold in order to achieve very fast cycle times, allowing you to produce more product. However, bear in mind that this will also require higher pressures.
Another big advantage of thermoplastics is that they can be easily recycled. This is becoming more important due to regulations and market demands. If you have a bad product or simply are replacing product that has been in the field for a while, all that you need to do in order to recycle the material is to chop the plastic up to where it is pellet sized, and then they can be remelted and molded into a new product with no loss of properties. Thermoset materials can only be chopped up in order to use as a filler product.
Thermoplastic composites also have superior impact and damage resistant properties. The use of thermoplastics as a composite is still a niche market, but this area is growing.