On top of that, proper deep frying requires enough oil mass to maintain the desired heat. Nearly all residential units don't have enough volume capacity to work as intended. Air-fryers though move heated air constantly replacing the need for oil mass.
I've got a countertop two vat deep fryer and it keeps the heat really well (much better than the single vat ones most people have). The problem is because it uses so much oil each time I rarely use it, so it sits in the cabinet 99% of the time. End up using the air fryer for everything.