The handle with the phone mount gives additional stabilization allowing for better angles and achieving a more professional looking image.
Given the high quality of newer phones, and some skill, you can film professional-looking fisheye footage with the Trabajando Fisheye.
Filmed on an Iphone 6s with the Traba handle setup.
4 By 3 Footage on the Trabajando Fisheye Iphone 6S With the Traba Handle
Filmed on an Iphone 6s handheld.