For context, LDAC is one of the few wireless audio codecs stamped Hi-Res by the Japan Audio Society and its encoder is open source since Android 8, so you can see just how long Windows is sleeping on this. I'm excited about the incoming next gen called LC3plus, my next pair is definitely gonna have that.
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I can only comment on my experience with my own equipment and ears, but in my experience, 990Kbps LDAC is noticeably more transparent than 256Kbps AAC for Bluetooth audio.
I can fairly reliably guess whether or not I remembered to switch my Sony XM4s out of multipoint mode the last time I used them (when in multipoint pairing mode LDAC is not supported and 256Kbps AAC is usually what gets negotiated). The difference is small, but over a few minutes of listening, the sonic signature when it's using AAC is just a little bit "off" and my ears don't like it as much.
Could I ABX the difference using the usual ABX setup with short samples of music I'm not familiar with? Probably not. Can I tell the difference over an extended period using music I know well, and that I often listen to uncompressed? Yes, pretty easily.
LDAC is not a particularly sophisticated codec, but it doesn't have to be when it has a 990Kbps bitrate. It's also possible that the FDK-AAC codec that I think both Pipewire and Android use for real-time AAC encoding is not the best tuned for 256Kbps CBR. AIUI in 256Kbps CBR mode, FDK-AAC has a hard low-pass filter at 17KHz, and I can still hear above 17KHz.
if you tested on android then I wouldn't be surprised, android is notorious for having sketchy AAC settings https://www.soundguys.com/the-ultimate-guide-to-bluetooth-headphones-aac-20296/
FDK-AAC on linux is considerably better, I dont think I did a bitrate mod on it but I may have? I think pipewire by default caps AAC at 320kbps and can hold it reliably, and at 256k both opus and FDKAAC are transparent to the vast majority of people even on high end audio setups.