For what it's worth, I have come to the conclusion that the Mavic is softer than the P4. This has been echoed by every (competent) person who has had hands-on time with the Mavic. However, this is a trivial point, because many of the people who do high-end (or even casual, like myself) media work from P4s turn down the sharpness in the camera settings, so now it's just one less setup step to do. And if you decide you want the extra sharpness, at least two folks I've seen have stated no issues running a post-process filter that makes the resulting quality pretty equal.
So the question people have to ask themselves (and themselves alone) is whether the tradeoff between form factor and maximum out-of-camera image potential is worthwhile. For many people I have come to respect, their answer is yes. I'm a hobbyist and I'm not trying to win any awards, so having something I can carry with me at almost all times is mind-blowing.
Nitpicking between the P4 vs Mavic has run its course at this point. If you have reservations about the Mavic, or have specific needs/desires about consistent and known quality, buy a P4. Even DJI even states in their FAQ (via the Go app) that the P4 is better suited for landscape photography, for instance.