P3P will support more features like ActiveTrack, Tapfly,Tripod Mode,Draw,Gesture Mode. And the camera of P3P is powerful than P3E.
P3P can shoot 4k @60 fps while PSE shoots 4K@30fps.
You can check more information through our website:
http://www.dji.com/products/compare-consumer-drones

The huge difference is that the P3P uses Lightbridge for control and liveview.
When DJI released their Lightbridge drones they made all old-tech wifi drones obsolete.
Lightbridge is 10x better.

The SE is an intriguing AC as it's the most powerful wifi AC DJI has made to date.  The SE is fairly new, released outside of China only a couple months ago.  The P3P OTOH was released about two and a half years ago.

Still, I would go P3P for the reason mentioned above.