Friends of ours swear by fibreglass pools. Faster to install. Cheaper. Smooth under foot. No calcium build ups if the chemicals are not balanced. I am sure there are negative issues that other folk can comment on. Our friends recently re-landscaped their back yard and replaced the old 20+ year old fibreglass pool that came with the house with another fibreglass one. They say they wouldn't have anything else. I only mention fibreglass as an option. I have no personal experience with them, but other seem to like them
my parents had a saltwater fibreglass in ground pool at their place for years, never had problems with the shell ever just eventual problems with the filter due to it's age. They filled their's in recently as it doesn't get used much now and the filter needed replacing, so thought it's time for it to go.