Excellent common question, let's break it down:
DC Motors (analog)
DC motors are analog motors, we can only send power signals (two wire) to the motor to drive them. This means that we can use predictions to figure out where the motor will be located over time within a relative margin of error (3-8%) but we can't know exactly where they may be located. For this reason sophisticated planned moves are tricky if not near impossible to achieve so it's best to build up more complex moves manually, in other words watch what's happening at the rig and make motion decisions 'on the fly' rather than 'pre program'. DC motor systems were relitively easy to develop around so we were able to develop our DC controllers in a short period of time (matter of months). DC motor systems are definitely a great for the budget minded shooter.
Our DC Controllers: MX2, MX3 and AT2
Stepper Motors (digital)
Stepper motors are digital motors, we actually send position signals (four wire) to the motor to drive them. This means that we can know exactly where they are at all times. For this reason even most sophisticated of a moves can be achieved, it also means that 'repeat' motion passes are possible because we can know exactly where the motor is located and have it return to a 'home or start' position precisely. So for example say we want the system to start and end at specific points and then we want the same motion to happen in a different timeframe, this is all possible with very precise accuracy. Digital stepper motor systems are more complex to develop and require a high level of electronics, programming and software, it's taken a lot more time and resources to develop our stepper controller (matter of years). Stepper motor systems will tend to be a little more expensive because of these development costs, particularly due to the increased software development costs (iOS, Android, OSX, Windows..)
Our Stepper Controllers: NMX