Compression drivers provide the upper range of the frequency spectrum, making a good choice here is often the difference between a bad speaker system and a great speaker system. some important things to remember is pro audio compression drivers are often much louder then the woofers so make sure you when you select a good compression driver that the crossover point often sets the power handling. if the crossover point is very low the power handling becomes worse, so if you want to set a low crossover point ensure you have high power handling and a horn to match the desired crossover section.
Compression drivers range in power handling between 20 watt to 100 watts respectively and are good at producing sound from 1200Hz to 20 000hz and greater, they are available with various fittings being bolt on and screw on to be couple with different horns.
The size of the compression driver is normally proportional to the lowest crossover frequency possible, 1" 20 watt compression might only be suitable to handle from 3500Hz and upwards vs a 2" 100 watt compression driver that could cross over as low as 800Hz.
In addition to the size and power handling capacity you have the added value of both Ferrite and Neodymium Magnets, some drivers also use different diaphragms for enhanced performance.