Pro Comfortable, clicky and intuitive to use
Though the controller feels light, it's solid and very comfortable to hold, especially compared to many other portable controllers.
The buttons on the controller feel clicky and the layout is similar to those of console controllers, making it intuitive to use. This is often not the case for portable controllers.
Pro Portable, like your Samsung Gear VR
The Samsung Gear VR set is portable. If you want to use it on the go, you need a portable controller. The Moga Pro Power is relatively small and can fit in your bag without taking up a lot of space. The buttons and joysticks almost don't stand out from the case and it has short palm grips.
Con It only slows down the discharge of your phone battery
The 1800 mAh battery charges your phone with 500 mAh output. If you're playing with a powerful flagship phone, the controller will just slow down the process of discharging.
As a sidenote, the controller can charge your phone only if it has at least 25% battery left.