I don't think I would call a captains chair gimmicky as it does have a purpose. But, as you said, it all comes down to fit.
Having sold Marquis from 2014-2017, I'm not sure I would agree with the more power aspect. I personally do not think Hot Springs has the strongest of jets, but as we all know, more power does not equal better therapy. I do think that Marquis allowed you to concentrate more power to an individual seat though and in the case of the H.O.T. Zone jets, they are stronger, but you are also turning off a lot of other jets to accomplish that. At the end of the day, it is a matter of personal preference. It's too bad your Marquis dealer had their flaws which resulted in you not getting another Marquis. Your Aria is a great hot tub that will provide you many years of enjoyment.