If maintenance isn't your strong suit, consider a tub with a self-cleaning option. Though, this is only available on the water jet systems.
The number of jets and placement is something to consider in your purchase as well. It's possible to add extra jets to target problem areas of the body, such as your back.
Tub basins can me made from many materials which will vary the size, shape and life of your tub. The most versatile material for whirlpool tubs is acrylic. Acrylic is easiest to customize for personal style. Fiberglass is the least expensive and the least difficult to install. If you have a little more to spend, a cast iron tub is the way to go. Cast iron is a tougher material and will have a longer life than some of the lower-priced tubs.
And finally, there are extra safety options such as slip-resistant coatings, rails for safe entry and exit of the tub and emergency shut-off features. These add a little to your cost, but it's worth ensuring the safe enjoyment of your whirlpool tub.