Irelia is different because if you crowd control Ahri, she is dead. Can't really crowd control Irelia because her passive gives her at least 10% tenacity, icnreased to 45% from Treads. If there is 3 people around, she has 75% tenacity. Plus she usually gets the Tenacity buff in the Defensive Mastery. You cant just crowd control Irelia to stop her, you have to win the stat war and out DPS her, which is hard since she has a lot of heals to make up for it and has a 2 second stun if you can out DPS her to put the battle in her advantage. You have to absolutely swarm her with your team, and that is costly to do since that still leaves the enemy team's Middle and Bottom to rampage. Irelia is also pretty tanky.
Ahri is great, but if you throw a stun on her, she is dead since she is really squishy. Thats the end of it nearly.