If possible, it is always best to try out hot tubs when they're filled with water and operating. A hot tub shell that seems comfortable and well-suited for your height when seated or stretched out will feel a lot different once you're buoyant and more weightless. Try out each seat, moving from each mold and curve, to see how it feels for you and how it will feel when shared with others. For example, see if the tub is roomy enough or if there's too much knee-to-knee contact and not enough arms spread across the edge room for your liking.
Jet power is important, and it may seem like "the more jets the better," but placement and functionality of the water jets really makes a difference. Check the placement and move around a lot to determine whether you will have to feel a jet every time you sit down! If they poke into you at every turn, comfort could be an issue, but make sure there is enough power to massage muscles and get the full effect you prefer and that the settings are adjustable and easy to regulate.