Pro Internal rechargeable battery
The Nyko PlayPad Pro lasts about 30 hours of gameplay per charge, and uses an internal rechargeable battery that is charged through a USB port. This is cheaper in the long run, and also generally more convenient than worrying about disposable batteries.
Pro Different modes expand the utility of the controller
Typically, you will want to stay in Game/HID mode - this is the standard Bluetooth controller mode. iCade mode can be used for games that don't support Bluetooth controllers, although the Android recognises it as a keyboard instead of a gamepad. This trick allows you to use the controller where you wouldn't be able to use other controllers, however you will be missing out on the full experience as some of the controls may be wonky or simply not usable depending on the app.
Mouse mode doesn't help much as far as gaming goes, but for navigating the UI it works well. The last mode is App mode which allows remapping of the buttons (requires root access).