I don't think there's any "gain", but there's possibly not as much downside as you're thinking. I just leave my adaptor plugged into my headphones all the time, so it's really no different plugging the lighting connector in compared to plugging a 3.5mm audio connector. More hassle if you have multiple sets of headphones I suppose (and I do, but only one cabled set that I use regularly, and a bluetooth set as well).

There's still a minor downside, I can't charge my phone with my (wired) headphones plugged in - but I can get almost 2 days without charging my phone (an XR) so that's never bothered me at all.

For me, the camera on the iPhone XR is _totally_ worth the "downside" of Apple's "no audio jack" decision. That's a very personal thing (I want great low light camera performance for band/gig photos) and it's not something I'd ever tell somebody else is an important purchase decision for them. Same for you, there's no way I'd try to "sell no audio jack" to you. But I might advise that whatever _other_ feature a specific phone has for your personal use cases might possibly override the downsides of no headphone jack.