We currently have a fiberglass pool and it has osmotic blistering of the gel coat that is quite extensive. The pool is about 9-10 years old. Don't know the brand (we bought the house with it). Pool is still structurally sound but there are places where the blisters are large and the gel coat has flaked off exposing the fiberglass underneath. The pool would need to be drained and gel coat ground off and repaired, so likely as expensive as a replaster if not more. Just wanted to point out that all is not rosy when it comes to fiberglass.

The house above we are renting and we are planning a gunite pool for our house. One builder we have spoken to said they just did a replaster on a pool where the original plaster lasted 17 years. A coworker has a gunite with plaster that is at least 20 years old and in good shape. Just build it well and take care of it and you will likely be rewarded.