Yeah, so the MacBook Air has a fan. It helps provide better performance because during high load activities, the fan cools the CPU to an acceptable thermal threshold whereas the MacBook has no fan and simply just thermal throttles the CPU at the expense of performance.
I did a couple of 4K video transcodes on three fairly new machines and here are their relative scores:
- Mac mini 2018: score 100
- MacBook Air 2019: score 146
- MacBook 2017 (i7 maxed out): score 223
Same OS, same video files (I encoded two different videos), same Handbrake settings (H.265 VideoToolbox). They were in the same room (same ambient temperature) and none of the systems were doing anything else.
So the MacBook 2017 took 50% longer than the MacBook Air 2019 but the former was silent. The latter was the noisiest of the three systems (fan around 5800 rpm).
The question really comes down to how much you value silence over performance.
Note that the Air 2019 has the T2 chip and HEVC encoding is done in hardware. The MacBook 2017 does it in software and thus will drain the (smaller) battery quicker.
I will point out that in normal desktop usage (office programs, web browsing, video playback, etc.) one cannot hear the Air's fan. Sometimes the fan is off (as it is right now).
The MacBook's performance is fine for tasks that don't tax the CPU.
At the risk of sounding like a broken record, I will flatly state that the MacBook Air 2019's keyboard blows doors on the keyboard of the MacBook 2017 in terms of comfort and feel.
The three primary user interface components that I use to interact with the computer (display, keyboard, trackpad) are all vastly superior on the Air 2019. Moreover, the Air 2019 has a second Thunderbolt 3 port.