We have been using a DJI Phantom 4 Pro for video and photography work since 2017 and it has worked out exceptionally well. The picture quality of both video and stills is amazing and we have been very impressed by the stability and maneuverability of the platform.
So why invest in the smaller Mavic Pro?
The Mavic Pro packs down into a very small space indeed. Way smaller than airline carry on restrictions allow. It is inconspicuous, quick to unfold and set up and in the case of the platinum, relatively quiet. This carries many advantages, it's a much more spontaneous device than the phantom and can easily be taken out on a hike since it weighs so much less.
At 30 minutes, the Mavic Pro Platinum matches the flight time of the Phantom. The range is equally impressive though keeping the Mavic within line of sight is more of a challenge. As a cameraman I'm more interested in keeping the drone in the air while I get the best possible shot. Working with people as we did on our recent promo for RideVentures can often mean five or six takes and that eats into flight time very quickly indeed!
The Mavic is smaller and in the hands of a good pilot easier to get into and out of restricted spaces than the Phantom (you'll need to turn obstacle avoidance off so take care!). This definitely helps to get cinematic footage that really stands out. Where a ground based gimbal can't deliver the Mavic often can.
I haven't so far found anything the Phantom 4 can do in software that the Mavic can't. 360° Panoramas, POI, Waypoints etc. all work in exactly the same way as the larger Phantom 4.
The camera is not as good as the Phantom and as a photographer this was the one sticking point for me. It's good enough at 12MP and 4k to deliver against most requirements. The Phantom 4 at 20MP is pretty close to my Canon DSLR at at 22MP. The one irritation for me is the sensor size which gives me 4:3 aspect ratio photographs with a 78.8° field of view as opposed to the Phantom's wider 84°. You may not think that 6° makes a massive difference but it does! I've learned to frame for editing.
Unlike the Phantom, The Mavic has a fixed aperture f2.2, which means that the only ways of adjusting the light are by increasing the shutter speed (to darken) or increasing the ISO (to brighten). Not ideal if you're used to manual camera operation but it has prompted me to use ND filters (Polar Pro Cinema Series) more often which gives me a lot more control over the look of the final image.
If the internet is your only outlet for video, then the Mavic Pro Platinum is an outstanding drone. It is perfect for travel and excellent for YouTube.
For us, as filmmakers, the DJI Phantom 4 Pro is the outstanding drone in the prosumer market and will continue to be the go-to filming platform for the foreseeable future.
However, if you're not planning on making videos for platforms other than the internet, I'd recommend the Mavic Pro over the Phantom because its smaller, lighter and easier to carry around.
A Word of Caution
In the UK, the exam for CAA approval (PfCO) requires you to perform manoeuvres in ATTI mode. The Mavic Pro does not have ATTI mode, so if this is your first drone and you're intending to make money, you'll need to practise (extensively) with a Phantom 4 at minimum.