The Spinfire Pro 2 ball machine is now used by pro's (on the way to the top) because of::
- High accuracy/positioning when shooting balls
- High degree of spin and speed
- Good and varied addition of training with a coach
- Lots of possibilities for desirable training
- Reliability of machine
- Easy settings of trainings (reproducible for next time) and many possibilities with remote control
For upcoming pros is continuous training with a coach a (too) expensive solution while the variation of "training with a coach" and a Spinfire ball machine indeed is a nice diversification for the training is.. Coaches who claim that a ballmachine-training is not a good training, are not aware of the possibilities and accuracy of a Spinfire ball machine which is also very suitable for pros (or they are afraid for their income :-) ). It's obsolete that a ball machine "plays not human", "has not enough speed for pros", etc. Sure, a ball machine has (especially tactical) limitations but for trainging of special strokes, getting rhythm, footwork, striking balls different (faster) is a Spinfire ball machine a great tool.
Above you see a video of Vivian Heisen (nr 750 of the world rankings WTA) where the ball speed is by far not the maximum.