Hi,
I had a Phantom and Mavic Pro, but bought a Spark to take on holiday in 2017 and for quick flights when out walking. It is a very good piece of tech, but range and battery power are a bit limiting. Certainly range, I was loosing video too quickly. That said, I still like the small size and speed to get in the air and was generally very happy.
This summer, I bought an Air and sold my Spark. The Air is better in every respect, flight time, camera, range and video signal. If you like your Spark, you will love the Air. The Air is not quite as good as a Mavic Pro, but it is smaller and lighter and if anything quicker to get in the air. Battery life and range are all acceptable and the new features on the Air, like forward and reverse sensors are an improvement over the Mavic Pro, but I am sure the
Mavic 2 has all of those. The Air is also well priced.
So if your Spark is in good condition, like mine was, you should get a good price for it as it is a great entry drone for someone new. I doubt you would want to keep both once you get an Air.
The bloke who bought my Spark, couldn't believe how good it was.