All the brands you listed are going to be considered premium, quality manufacturers. However, the models you have listed will vary in terms of being high end and low end within each company. The Hot Spring Jetsetter NXT, Bullfrog AL5 are top tier from each company and the Jetsetter, RL5, J315, and Santa Cruz are technically a step down. The Iris is really entry level from Artesian and with Sundance, I would be using the Capri as a more comparable model.
Check out each dealer, they are almost as important as the hot tub you choose. I think fit is really important, and more so on smaller spas. Dry test each and once you have narrowed down your list, wet test to see which you like best. I would run 220V since you can run the heater simultaneously when your jet pump is on high speed.
