I have used the following Servo Control Boards. All have their strengths and weaknesses: I believe there are other offerings but I haven’t used them as yet. These are just my own personal opinions as a user.
GF Controls Dual Servo Controller Board:
Most expensive of the 3.
Cannot alter speed or bounce characteristics.
If you want to, you can reverse the direction of operation but not individually.
Easy to set up
Needs special power supply
Can be confusing to set up
Cheaper than GF Controls per arm
Can be configured exactly how you want it
You have to be a member
Special Firmware has to be written to the Micro processor to enable bounce (SEMA4)
Bounce feature as standard is not in my opinion as good as the other 2
Need a Windows PC to set up
Cost - cheapest of the 3 but you have to build it from a kit
A variation of the SEMA4 firmware is available which will give a simulated bounce similar to the other 2. You will need a Pickit 2 or Pickit 3 to write the code to the PIC.