Also, FLAC file decoding is horribly slow - compared to the FOSS reference decoder -, because for some reason the whole file is scanned through on the first read when using the AudioFile APIs (AudioFileReadPacketData). (I’m gonna make a demonstration project for this and send them a bugreport tomorrow.)
With Apple’s AudioFile API you can decide whether you want the decompressed PCM samples, or the underlying compressed packets. You can get better energy efficiency if you offload the decompression step to the dedicated coprocessor. The difference is smaller than with hardware vs software h.264 decoding, but there is a difference.
(For lossy codecs this also makes sense when you want to forward the compressed packets to a wireless speaker in order to avoid lossy recompression on Bluetooth transmission.)