First, the forced air cooling should be used with an adapted handpiece. That solves the problem of either needing multiple people or making it operator dependent. In other words if the handpiece is used properly, then the air cooling is consistent. If they aren’t using a handpiece then they are doing it wrong.
Second, the problem with cryogen is that it is short. If it is too long a pulse, then you burn the epidermis but if it is too short then you don’t effectively cool down the basal layer of the epidermis. This is the deeper layer. Cooling isn’t just a function of how cold something is but how long the cooling occurs. This is why you can run outside for 10 secs when it bitterly cold outside and you don’t get cold and you can get chilled to the core sitting in a room at 65 degrees for a couple hours. The air coolers have much more dwell time (time spent on the site) than cryogen and are therefore more effective. This by the way, has been proven using pig skin and temperature probes.
Finally, it has been shown that it is impossible to cool down the follicle (which is buried deep in the dermis) using normal cooling systems. In other words, the zone of cooling is limited to the epidermis and the upper dermis.