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Besides quality of the spa, longevity, insulating ability, hydrotherepay, etc. there is another major factor IMO. The big box spas may come with a warranty (that varies but isn't always the greatest on paper) but where it really falls short is when there IS an issue there is no dealer to call to come over for service. You will hear that you only need to call some 800 number and they'll find a service person in your area but that is hit and miss. Some have reported that an indpenedent service person came to fix the spa but sooo many have said that they end up becoming their own service person out of frustration so if you're not a do-it-yourselfer I'd think twice and even if you are it sure is nice to have a the dealer take care of the warranty work as expected. Your mileage may vary on this subject.