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On the P3, the one on the front of the aircraft (in the plastic shell) is used to access the uSD card (this card cannot be removed) that is inside the P3, on its main ESC board. It can be used to retrieve .DAT flights records. Normally such files are found in your tablet but in case of radio disconnection or RC failure, it allow to get the flight record for further analysis. But this require to put the P3 in a special mode with the RC.
On the P3, the one on the side of the camera (aluminium) is used to access the uSD card of the camera. This is a slow way to retrieve videos.
On the Remote Controller, the mini-USB seems to be of no use, probably at factory only or for some future use?