There are generally two types of speaker selectors: resistor based and autoformer based. On one hand, resistor-based speaker selectors are generally lower in cost than their Autoformer counterpart. Resistor-based speaker selectors cost manufacturers less to build, and work quite efficiently and acceptably for background music applications.
On the other hand, autoformer based speaker selectors are far more efficient than resistor-based selectors. For the die-hard audiophile, nothing less will do. With these selectors, you get increased highs and lows in your sound levels.
A good rule of thumb when deciding on which kind of speaker selector you want is to match it with the type of speakers you are purchasing. If you are planning to spend $200 or greater for a pair of speakers, then you should get an autoformer based selector to make full use of your speakers’ potential. If you are spending less on your speakers, then you’ll probably be fine with a resistor-based speaker selector.