I'm encoding audio files from AIFC to ALAC using ffmpeg, I noticed that ffmpeg provides two different encoders for this purpose, named alac and alac_at:

$ ffmpeg -encoders

 ...

 A..... alac                 ALAC (Apple Lossless Audio Codec)
 A....D alac_at              alac (AudioToolbox) (codec alac)

 ...

I understand that alac_at is based on AudioToolbox which is a native Mac OS framework for manipulating audio streams. But I don't really get the difference with the alac encoder from my end-user perspective. I could not find detailed and accessible explanations on this topic.

The most important aspect to me is the compatibility of the resulting files, and secondarily file size. So could you please guide me on which encoder to use and why ?

Thank you