is think about avoiding one where the insulation is sprayed-in, fully encasing all the piping around and under the tub. I know it is more thermally efficient that way, but the pennies you save in operating cost will come back to bite you later.

Unless you don't plan to keep it longer than five years, it will leak sooner or later. Digging through spray-in insulation to find and fix a leak will make you want to scrap the tub and buy a new one (or never own one again).

That said, I don't even know if you can buy a spa that doesn't have spray-in insulation. They may all insulate that way. But it is worth looking for/asking about.

No real recommendations on a brand or where to buy other than from someone local who services the unit themselves and doesn't subcontract.

Finally, buy your chemicals at Lowe's / Home Depot and not at the spa store. They are almost half the price.