Owner of a Phantom 2 and Phantom 3 Advanced here. I say that because the P3 has a huge advantage over the P2, an integrated light weight camera system. My P2 is designed to swing around any number of GoPro action cams. Those cameras consist of all the processing electronics, battery, wifi and all the support necessary for a stand-alone camera hanging on the end of the 3 axis gimble. What that amounts to is large stepper motors and support arms able to swing the weight of the camera around.
On the entire P3 series, the Phantom 4 and the Mavic DJI has wisely split the camera in to what amounts to an image sensor and lens at the end of the gimble connected to the camera circuitry on a board above the gimble. No additional battery required to run the camera either. The motors and arms can be much lighter. This makes the camera even more stable and prolongs flight times.
The down side is you can't readily upgrade those cameras. I'll take the trade off as I'm much happier with the design of my Phantom 3. The Mavic looks to be a compact little beast of a quad. If I didn't already have a solid aerial camera platform it would be my first choice at the moment.