The best thing to do is install and compare both.
I will not found many AIR specific features (or event anything besides IDEA-127053).
I used IDE 14 (very old) on MacBook 2011.
Comparing version 14 and 2018, both takes around 10 minutes to build (we can't count seconds).
With MacBook 2011, IDE 14 took exactly 30 seconds and MacBook 2018 took exactly 20 seconds, so I got around 30% performance improvements and it's a good reason to update.