Mobilexcopter
you're right, flixed wing aircraft (manned and unmanned) capture extremely good and sharp images all the time... but they're not 1.5kg ans as good as stable as the Phantom 4's are (and they are amazingly stable) they are more susceptible to a small gust of wind than an aircraft of a few hundred kg. On saying that a phantom 4 is just as susceptible to a gust of wind when hovering than moving, it's just that if you can remove any movement from the aircraft, why not?
I am impressed with the 20mpix camera on the Phantom 4 pro, I would like, for my work, a little longer focal length than the 8.8mm (24mm equiv) but it's yielding phenomenal point clouds and othophotos all the same. Sure there's no interchangeable lens but then we have complete freedom of height (up to 120m agl of course) so I've had no need for other lenses. Videographers would have other needs/wants but's not my game
I agree with Yoann as far as app's are concerned, I've tried many (not all) but DJI GSPro does at least as good as anything else, it's free and you have control over camera/aircraft settings ... and for me, very reliable ...which is my primary concern.