In my opinion, your local options are your only options. A hot tub is a big purchase and all of your premium brands only sell through a network of dealers. If you can buy it online, you are likely dealing with a low end manufacturer and you're not getting much if any support after the sale.
With that being said, I am a Hot Spring dealer. Your quoted price on the Rhythm is a bit less than my price and I charge a $3k premium for the Flash. Depending on your wants and needs, the Flash can absolutely be worth the difference or it may not be. If you value the better therapy and more control of your therapy, then the Flash may be for you. If the better energy efficiency, longer warranty, or saltwater compatibility are important, then the Flash could be for you. I would need to know more before I could say the Flash is better suited for you. What are your expectations from the hot tub?
Brand preferences aside, you should buy the hot tub that best meets your needs. If you don't know your needs or either brand could meet them, then buy from the dealer who is more trustworthy.
