TECO units are good quality. It was mentioned above, but just to reiterate - you need to re-wire the saw's switch to be a control input to the VFD - if you use a switch wired between the VFD and the motor you will very likely damage the VFD's output stage.
A VFD is the best choice for single-motor machines that aren't too huge (cost reasons), and for any machine that may benefit from varying the speed - drill presses, lathes, etc.
A rotary converter is the best choice for multiple motor machines or multiple machines, and may be more economical than VFDs depending on motor size.
A static converter is the last ditch choice you only take when money is pretty much the only factor.