Background Reading: 3-U: Horsepower and 3-V: How Many Pumps

Tips:

-keep in mind that horsepower doesn’t determine jet strength – lots of other factors come into play that matter more.
-If it’s a high-end brand, you can rest assured they’ve done the engineering to deliver appropriate pressure to each jet. 
-If it’s a cheap brand, either ask for a wet test, or roll the dice and resign yourself to whatever it may be.
-If you like the idea of having two separate arterial systems, one for each side of the tub, then go for 2 pumps.
-I recommend avoiding 3 or more jet pumps – it’s noisy, needless, and there’s more to go wrong. 
-get a circulation pump if you enjoy sitting in the hot tub in silence – otherwise, don’t bother, as it won’t save money on your power bill or clean your water better.