Since they don't technically fry... Or do they? They're basically mini electric ovens. What's the difference between an air fryer and an electric oven, other than size and energy consumption?
There's some marketing going on, but they really do blast that air hard in a way that convection ovens don't. It makes a difference because food gets a lot more external heating at the same temperature compared to a convection oven.
The biggest win I have found so far for the air fryer is reheating leftover fries, like from a take-out meal.
In the air fryer, the fries wil go from fridge-limp to perfectly crisp but still moist inside in 4-5 minutes. In the convection oven, by the time the fries are crisped, they are dry.
I definitely prefer the air fryer for that task, and other similar things.
In the convection oven, by the time the fries are crisped, they are dry
Put them in a colander, give them a good rinse under the kitchen tap to get them wet all over, then tip onto a tray and into a preheated oven at 200°C for 10 minutes. Arguably better as leftovers than originally.