The only reason why you should risk something with a "poor" dealer, is to get a better price. Prices being equal-ish... why would you want to even risk putting yourself in a situation where you cannot get service?
All of the spas you mentioned are copied off each other. The Rhythm came first (made by Watkins,) then the Vanto (made by Watkins,) then the Edison a few years later. All similar in quality and feel being as they copy each others designs.
We primarily deal with the Hot Spots (Rhythm version) which doesn't have dedicated cup holders like most of the Hot Springs, they just have a flat bar top so you can put 20 more cups then anything with cup holders. Hot Springs high-end line, the Highlife, doesn't have cup holders either, but again just more flat spaces.
I guess it's what is important, but I just wanted you to know that you can fit far more cups on that than one with dedicated cup holders.
Either way, I'm sure that dealer doesn't care if you get the Vanto or Rhythm!