There are several types of car glass insurances.
There is a full vision coverage where the kind of damages to the glass covers all sides of the car.
There is also a partial coverage where only a specific part of the car glass is covered.
There is an insurance policy that would cover only the full replacement but not the cheaper repair.
It is still best to consult the agent handling the insurance and compare the policies with other glass repair insurance companies.
As the owner of the car, you have to ensure that the coverage of your insurance will include all accidental damage done to the glass as well as any damage that resulted from all kinds of collision with another vehicle.
The final decision for the car owner would all depend on their needs and the probability of getting their car's glass damaged.
As the owner of the vehicle, you should asses the area where you usually drive and see if there are lots of stones in the area or vandals that can possibly damage your car's glass parts.
If there is no issue with the monthly payment, it is best to have the whole car insured for all types of damage to its glass parts.
The glass repair shop would usually offer to have all of the paper works handled seamlessly.
All the reputable ones take care of this little detail to ensure a smooth experience on your part.
Sometimes the premium is also bigger than the amount of repair cost.
In this case, the excess amount would be waived by the insurance company.