alt Hacker News>(MP3 is in a similar place. AAC and Opus are technically superior, but everything supports MP3.)
Actually MP3 is more like the H.263 / Divx here. AAC-LC is more like H.264. The difference in support of AAC-LC and MP3 is near zero, both in terms of hardware and software. While AAC-LC is vastly more superior. AAC-LC has been declared patent free ( all patent expired ) by Redhat for 9 years already.
The only part that is not perfect is there isn't a decent open source AAC-LC encoder. While you could use QAAC using Apple's encoder in iTunes. It would still have been better if there was an open source version. Luckily we just have a new AAC encoder with FFmpeg, it is doing great for and although sill not Apple's quality. But hopefully improve in the future.
Or Apple could have just open source the god damn thing.
I was under the impression that the new FFmpeg nmr codec indeed outperforms the Apple one in every bitrate with Google's new Zimtohrli benchmark as well as ViSQOL. That would suggest Apple doesn't really have to open source anything, we should be good?
Still, I don't see the point. Unlike video, audio decoding is so cheap you can practically do it on software even on fairly constrained devices. So really only in places like Bluetooth headphones where codec complexity can have a direct impact on battery life does it actually factor in. I say for most purposes people should just be going Opus today: it is far ahead of basically anything else. In most cases, for old devices you can simply ship software codecs instead.
Hell, Wikipedia ships video software codecs in the form of ogv.js, mainly because a lot of Apple devices wouldn't expose VP8/VP9 support even on SoCs that had hardware support for it, and that works surprisingly well. So for something like Opus, obviously it is trivial even on older hardware, even in the confines of a web browser. (And of course, Wikipedia uses it for Opus as well, but my understanding is this is only necessary for 1-2% of Internet traffic since most devices/browsers support Opus these days)
That may leave some niches where AAC-LC is still a reasonable choice, like maybe old PMPs. However, I reckon that there are probably a lot of older PMPs that in fact, don't natively support AAC. For example, the trusty Sansa Clip+ from 2009 doesn't have AAC support. If you were to install third-party software such as Rockbox, well, then you'd have Opus support.
So for audio, I think barring any specific reason not to, the meta is to basically always choose Opus.