The 1200 is a little small. I was looking at one for myself for when I head out to shoot and there is a possibility of bad weather. I have the 1200 I use for a small camcorder and 2 batteries, and it doesnt look to be large enough to 1) have room for padding on the sides (I like 3 squares minimum) 2) have enough room for controller, charger, 2 extra batteries.
The 1400 should have enough for the drone and controller and maybe a battery or charger. 11.81 x 8.87 x 5.18 (
LINK)
However, at least for me, the 1520 will have enough room for the drone, controller, 3 extra batteries, charger and car charger and hub, at least an iPhone 6S+. There should also be room to have a smaller SD card case as well. It is the one I will be getting as soon as I recover from the purchase fright of the Mavic. 18.06 x 12.89 x 6.72 (
LINK)
This is all supposition, since I dont have the drone and parts to measure, but just going by the case I have and the stuff I ordered. I need an all-in-one for this case for the travel outside of my norm. I have the Fly More package, so I will be getting the padded bag anyway, which will work most of the time.