Just in case you're not familiar, Paddock Pools has been in Arizona for a LONG time. I grew up in the Phoenix Metro area back when.
Anyhow - Hot Spring, Caldera, Sundance are the good brands in my opinion. There are other major spa brands that work well too, but those would be my suggestions. It looks like Paddock Pools sells Caldera and Sundance (though I'm not really a fan of the Bullfrog spas they sell).
Yeah I was in just a Paddock store last night, am going to the actual manufacturing plant today.