Even with an expensive convection oven I can't get things to come out as good as they do with an air fryer. The small area through which the warm air circulates is probably the reason. The fan in my air fryer is the same size as the fan in a household oven with convection options, but a much smaller volume of air.
Most people don't actually have convection ovens. Whoever wrote that post probably doesn't even understand that there's a difference between a convection oven and a traditional oven in the first place.
The things that consistently come out better for me in my air fryer (with less cook time) over the traditional oven are:
Home fries
Bacon
Salmon
Chicken thighs
Any vegetable
Leftover steak
Leftover pizza
There are actually very few things I care to use my traditional oven for, it's all just quicker and comes out better in the air fryer. Pretty much anything where you want it to be browned/crispy without overcooking the inside or using a ton of butter will be better in the air fryer.
Because it’s not just a convection oven that’s needed, it’s also venting the moisture that comes off the product being cooked. It also needs to be powerful enough to keep the temperature up while that moist air gets exchanged. That’s a lot easier with a small cavity like an air-fryer than a regular sized oven. Commercial combi-ovens can do the same thing, and maybe there’s some high end consumer models available, but it’s a lot easier on the pocketbook to get an air fryer than a full size oven. I’m not totally sure, but they might also use impingement(concentrated streams of hot air, as opposed to just regular convection), which is another thing that’s available commercially, usually in pizza ovens or things like the merry-chef/turbo-chef(Subway’s sandwich toasters) but not common in consumer equipment.
Haha yeah it's tasty and effective for sure. I just find it a little too filling when I'm trying to bulk up and eat more protein so I use a Misto sprayer with either olive oil or canola oil. I've had the air fryer set off the smoke alarm a few times when I used butter so I prefer the oils with a higher smoke point.
In the vast majority of convection ovens the heating element is on the bottom. In airfryers the heating element is on top and it circulates the air a lot faster.
They are actually making convection ovens with an airfryer mode now, where it uses a heating element on top and has a more high powered fan.
The household ovens with convection settings that I've seen had the fan at the back, in addition to the radiant heating element at the bottom, but I definitely found the air fryer to be better.
I don't know where you live and which ovens are common in your country, but convection ovens are the cheapest and most common thing in Europe. "Regular" oven mode is usually an extra feature for extra money. This is because convection is more energy efficient and the EU has strict efficiency rules.
I have seriously thought about buying a second air fryer because there are quite a few things that it's completely better for, the problem I run into is trying to do larger meals (5+ people.) You either have to do batches which means more time actually engaged in cooking, or you have to break some things into the oven, and some into the air fryer.