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Nice but not needed. Nothing is going to keep insects out. All spas even those with abs or fiber glass bases have ventilation openings where critters can and will get in. Jacuzzi was the first ,and only company for a looong time to put a fiber glass base on their tubs. About 7 years ago they switched to abs plastic because it is less expensive and more durable. Any way you look at it I don't think that should be a major factor iin your purchase. Jets, variety, placement and performance, and service from the seller are vastly more important. Good luck.
I see your argument, however I have a counter. Cars are safe without air bags. An air bag does not guarantee that you will survive a car crash. Does this mean airbags are pointless? I know we are not comparing apples to apples here but the cost of an ABS/fibergalss base is not nearly as high as an airbag either. It is an extra form of protection.I do agree with you that there are more important factors to consider, but I do not think that the feature is without value.HTMan