I used to sell Marquis and now sell Caldera & Hot Spring.
The Vegas has a lot of multi-level seating (deep seats are really deep and shallow seats are pretty shallow). It has a large open footwell and in my opinion, it, along with the Marquis e750 are the most spacious 7' spas I have ever seen. Its tight, but you can legitimately fit 6 adults. It has 50 jets with diverter valves so you can redirect water pressure to different jets giving you more control over your therapy. The downside is that this spa does not have much of any insulation so its going to cost more than the Vanto to operate and the filter is tiny which will require more frequent cleanings and longer filter durations.
The Vanto is much better insulated and has a considerably larger filter than the Vegas which I think those two reasons alone make it superior. There are less jets (35 vs 50) and you do not have the diverter valves so there is no way to increase or decrease water flow like the Vegas. I like the foot dome in the Vanto. It provides foot therapy which for the most part is lacking in the Vegas but also provides a place for you to brace yourself if you float or slide out of the seat. Vanto also has the inline spa frog where the Vegas does not. Everyone has their own opinion on water care. I like the inline system with @ease and that is what I sold on all Marquis and what I sell on Caldera.
Warranties are pretty much identical. I think the price you are getting on both is a fair price. I used to sell the Vegas at $6299 with white shell and black jets or $6499 with acrylic upgrade and stainless steel jets. I did stop showing any of the Celebrity series Marquis though due to that lack of insulation. As for the Vanto, I sell at $6499. I include polymer steps and prolifts will all Vacanza series Calderas. Don't get the stereo. Stereos are the first things to fail and while you are getting a good price on the stereo, either save the money or put it towards more hot tub.
Flair has the lounge which the Vegas and Vanto do not. Only you can decide what is comfortable to you. If you like the lounger and the Flair, then I think the $2k is worth it. You get a longer warranty (5 vs 2), 24 hour circulation pump, and upgraded electronics. You have ACE compatibility, more lights, more therapy than the Vanto, and I like the 20/30 split breaker system. $8500 is also a pretty good price.
If you like that Vegas, at least step up into a e750 from Marquis. You are spending more money, but you get more insulation, dual filters, larger pump 2, an extra year on the warranty, and if you order, you can choose the spa frog inline system, full foam insulation, twilight lighting, etc.
Research your dealers, they are almost as important as the brand you buy. Sit in the spas dry to see if they are comfortable and if you have the opportunity, wet test.
