Maybe I don't have well-trained ears, but my Air sounds fine coming from 16 Pro Max. The only thing I notice is it doesn't get as loud at max volume, but I almost never need it at max, so it was definitely a trade off I was willing to make. I've made speaker calls here and there, not often, but I honestly didn't notice any audio quality difference coming from the 16PM. Maybe if I did speaker calls more often, I would notice.
I also might not notice because I just don't expect great audio from phone speakers in general--because 1) they're tiny speakers on a tiny device with a tiny screen--I just want to hear what I need to hear, I don't feel the need to be immersed or anything, and 2) the only places where I ever use my phone on speaker is in private, which means either home, work, or car--where it is usually quiet so there are no issues with volume--but if it is noisy, or if I want better audio quality, in those places I have much better speakers that I can Airplay/Carplay to. Everywhere else I use earphones (I always carry a tiny mono BT headset in my pocket, or I'll bring Airpods or other headphones if I know I want really good sound or noise cancellation).
For me, the speaker is a complete nonissue, as is battery life. I honestly wouldn't even be able to tell if the Air got worse battery life than my 16 Pro Max did if I didn't read the specs, but that might just be saying more about my usage. The Air is really for me. It's worth repeating:
The Air is not for those who are conscientious about battery life on modern phones, who often use the ultrawide or telephoto cameras, or who care a lot about phone speaker quality. They may be tempted by the Air's ergonomics or aesthetics, but they will ultimately be disappointed.
The only trade offs I actually notice and don't have perfect (for me) solutions are the lack of telephoto and DisplayPort (few people seem to mention that one), but I use neither often, so I'm able to get away with workarounds. For the telephoto, I got a small superzoom camera to bring on occasion. For the DisplayPort, which I sometimes use with my XR glasses, I use my iPad instead of my phone. These aren't ideal but good enough. The amount of relief I feel daily using such a light thin phone more than makes up for it. I suppose it's all a math equation.
