The biggest advantage for having a good AAC encoder isn't efficiency, it's that for nearly the past 2 decades the de facto standard for live streamed video has been RTMP with H.264 video and AAC audio. There is basically no support for any other codecs. If you want to send a video stream to Youtube or Twitch, you will be sending H.264 and AAC. If you want an idea of how ubiquitous this is, I just checked in OBS and it will not even let you select different video and audio codecs in streaming mode, it just (correctly) assumes that anybody who's streaming will be streaming H.264 and AAC.
Also the fact that hardware-accelerated AAC and even full AAC offload is ubiquitous in modern-ish hardware. I think my rice cooker can play AAC audio
I think often of how all it would have taken was a bomb for the 10 or so people that years ago at some browser vendor consortium out of pure self centeredness went „nah lets fragment“. We could have saved many many collective years, electricity and eyeballs simply watching the most basic content.
Sample accurate editing is with AAC is a pain though. Especially if you also have video, because frame rates are usually incompatible.
If you want flexibility without fully transcoding both audio and video, Opus is your friend
Plus, at 96+ kbps (assuming an Apple-quality AAC-LC encoder) Opus loses its quality advantage. So at higher bitrates, the benefit of choosing Opus is that encoders/decoders are royalty-free.