What size pool is yours compared to your IL's? Do you guys have shade sail? We have a fibreglass pool, with shade sail and solar heating. Our pool is approx 9 x 4.5 in size and the shadesail covers about 90% of the pool and between Oct - Mar we don't need our solar on at all. So for us up here in Cairns, a fibreglass is perfect.
Ours is HEAPS bigger than theirs. Theirs isnt too big, but its a b!tch to heat!!

No shade sail... yet!!! Only been here 6 months, but we want one!!

Its a big pool, 15 x 4m. Takes up the whole of the main back yard. Luckily we have a side section!! Its good for laps. We'd use the heating about the same.

Maybe fibreglass is good anywhere!! I know the IL's hate their concrete one with a a passion, and the heating costs are just staggering. Its solar, but having the heat pump on all those hours for months is so super exxy.