alt Hacker NewsA fanless CPU needs more, lower-clocked cores to have the same multi-thread performance as an actively cooled CPU with fewer cores, and higher core count CPUs cost more. So you only get a fanless CPU if you either a) get a low multi-thread performance CPU or b) pay for a high-performance CPU and then get only medium performance out of it by running it fanless. Notice that even Apple's highest performance laptops have fans; fanless there isn't a thing.
But Apple's fanless machines do b) and then they just charge you the premium. There are a few fanless PC laptops that do the same thing, but most people don't want that, because they'd rather save a significant amount of money by getting the same performance out of a less expensive CPU with a fan.
This is oversimplified. It is sustained multithreaded performance that brings throttling with fanless cpu. Anything for a short enough amount of time is fine, and sustained single threaded stuff is also fine. Bursts are also fine. A lot of work that people do on a computer is fine. Fanless doesn't really hurt unless you process large amounts of data in parallel for some time. Performance in a cpu does not only show in this kind of tasks.
I have used both airs and the max versions of macbooks, and the airs are embarrassingly on par for too many things. I understand it may be hard to believe, but one can do actual, serious work on a macbook air.
Of course one could say that ~having~ using the fan is always optional anyway (like the older 13" macbook pro was mostly an air with a fan) and in these types of tasks you may barely hear it. But still I prefer the peace of not ever hearing a fan for my to-go laptop.