I have both the Phantom 3 Standard and a Spark. My P3S is 2 years old this Christmas and my Spark will be one year old at Christmas. When I got the Spark, the Mavic Air wasn't out so the choice was easy for me because I wanted a compact drone to complement my P3S and the Spark fit the bill. I take mostly photos with my drones and occasional video so the Spark was perfectly suited my uses. I love my Spark and with the Portable Charging Station, it is a perfect hiking travel drone. It is the only drone that can be docked via the charging station.
When the Mavic Air came out, I started thinking about all the features it has that the Spark doesn't (3 axis gimbal, ability to shoot RAW and some other extra camera features, but then I looked at the price and got a reality check - for what I need right now the Spark is perfect and what the Spark can't do I can usually do with my P3S. My next upgrade will likely be a
Mavic 2 Pro as I am interested in image quality.
So like PhantomFandom said it really depends on what you want to do with the drone. Do you need all the extra features the Mavic Air has for twice the price of a Spark? If yes, then you have your answer.
Chris