Azir is straight out stronger right now, for everything else than roaming. He deals a lot more damage: 3 soldiers have 90% ap scaling, while Aurelion stars have 52,5% ap scaling. Azir attacks faster and have a higher base damage. He has great mobility and can avoid ganks with E while Aurelion mobility is cancelled by damage, even though it makes you able to roam quickly. He has good lane pressure all the way from level 2 and scales very well into mid-lategame.
Don't forget that Azir also has some of the best objective damage for midlaners with massive attack speed, both to turrets and monsters. He's also a beast in siege situations with the zoning and passive. I haven't really been playing Aurelion, but I find Azir to be a lot of fun and already got a 61% winrate with him on the way to diamond. He's basically freelo, and even better once you get really good at him.
Aurelion shares some of these strengths, but in this meta and with the current damage numbers he is outclassed by Azir.