There isn't a one-size fits all version for all users and there are lots of funny terms. What does it all mean?
The PTZ Fly is great for 3 axes of analog control on the joystick (Pan/Tilt/Twist). To move a 4th, or 5th, axis, you are attaching this to buttons which can be fine for jogging, but not live control. If you are primarily looking to set up presets and recall them, this is a great controller for single or multi-cams. If you need live and feathered control of each axis, then the PTZ Extreme might be for you.
The PTZ Extreme is much bigger and in addition to the Pan/Tilt/Twist joystick like the Fly, it adds a zoom rocker, and two stepless knobs that can be attached to other analog controls. If you need live and feathered control of each axis, then the PTZ Extreme might be for you.
Bluepill or Unisketch - eMotimo's take
Unisketch is Skaarhoj's older model of control. In short, it's an 8 bit microcontroller where all the cores or API's to control devices are added from their programming interface. The controller then sends network commands to attach each device in a one controller to many configurations. If you are only going to add a single controller and want to connect multiple devices or cores, Unisketch is fine. Development has halted on adding and updating cores and API on Unisketch so Skaarhoj is pushing new customers away from this platform. In fact eMotimo is unable to update its published cores for controllers on Unisketch as they devote their resources to Bluepill.
BluePill is, in short, a Linux server that is either standalone or incorporated into many controllers. This lightweight server treats each controller as just a series of buttons and knobs. The server listens to outputs from the controllers and then decides what to do with those actions using a mapping/triggering web interface called reactor. This is new, and in many ways, its still being built out and ramped up. eMotimo has been developing our BluePill device code over the past 6 months with Skaarhoj's assistance and its starting to look good.
Why the transition from Unisketch to BluePill? Expandability where complex scripting of multiple controllers, really an unlimited number of devices talking, passing control, and speed are some reasons. For example, if you want CameraPerson A to be in control of eMotimo ST4.3 A/B most of the time but let camera person B on another controller take over control - this architecture support this. This is impossible in Unisketch as devices were attached to a single core.