Would you go as far as to say that the
P4P series is more of a "photographers drone" than the Mavic? I guess you have to sacrifice something depending on what your mission is, but to me, the flexibility of the camera and obstacle avoidance are it's strong points and the lack of portability is its weakest point. The OP is looking for "good quality 4K footage" and "reliability" and has already said he is willing to forsake portability to obtain his goal.
It's a testament to DJI that given the completely different designs, prices, and features of the Mavic vs.
P4P that people have trouble deciding which to buy. DJI has stepped their game up so much in the recent past, that you dont have to sacrifice a huge amount of quality for portability, But if you want to go beyond what the mavic is capable of, you can get the
P4P for not too much more money and have drone you can hang on to for a long time and use professionally with its advanced camera features.