Sundance and Jacuzzi are owned by the same conglomerate, so you're buying a good brand there. Hotspring is Jacuzzi's #1 competitor by volume. (Bullfrog would be the #3 largest brand name on the internet, so be sure to take a look at their offerings while you're at it)
I'm a new spa owner and naturally a fanboy of my brand, so my vote is for Hotspring haha. But you really need to wet-test both the Sundance and Hotspring spas to see which you like better (even if the make/model you want isn't available, at least wet-test another model from the same product line to get an ideal comparison). Not everyone likes a Motomassager on the HotSpring Highlife spas. And by the inverse some might find the Sundance jets too strong or irritating for one's liking.
Wet testing is important, but also be sure to review the dealer - they will be your point of contact for all warranty service so make sure they're competent. Not all spa dealers are created equal - some budget brands and dealers expect you to be your own service technician while other dealers will give you white glove service from purchase to five years later with zero call out fees. Prices for the same make/model can vary greatly even within your region depending on the dealer you're buying from, so don't be afraid to call other dealers in your region
