The "clicking" occur when you allow the pump to completely shut down. The clicking sound is when the pump initially re-start. If you turn down the pump to 1%, you will avoid the clicking sound. FWIW, Vortech doesn't allow their pump to totally shutdown in any of their mode on the controller. The motor is always spinning. If you do this with your Tunze, there will be no clicking sound.
Any Vortech pump will be louder than an equivalent Tunze period.