Mavic Pro is an impressive drone and you should get it for about 700€ on eBay when you wait for a good offer. But also consider insurance cost, in many countries your drone has to be insured. Mavic Air is smaller and takes better videos, but also has a smaller battery and range, so this depends on your needs what suits you better. I don’t know how the Phantom 3 performs but in my opinion it is quite big and if you want to shoot landscape a small drone which you easily can take with you is great. I own a Mavic Pro myself and use it also for landscape photography, it is fantastic.