Is there any actual difference between them all or is it just additions of pretty colours?
250 Hz Classic - no LEDs, no RPM Counter
Neon Blue Pro - blue LEDs, RPM Counter
Neon Red Pro - red LEDs, RPM Counter
Neon Green Pro - green LEDs, RPM Counter
Signature Pro - white LEDs, RPM Counter
Fusion Pro - fusion LEDs, RPM Counter
Techno - red and blue fireline LEDs, no digital RPM Counter but there are LEDs integrated in the actual rotor. After a high speed run, the score shows up scrolling across the actual rotor face. It's tricky to do properly.
All of these Powerballs are 250 Hz (meaning they are calibrated at 15,000 RPM) and function in exactly the same way, offering the same workout. The choice is in colour, LEDs, RPM Counter and whether you want the special counter of the Techno. I would recommend a Neon Pro, Signature or Fusion which are all basically the same but with different coloured lights.