I haven't done or seen any tests, but I suppose if you require VBR and/or HE-AAC support, go for libfdk, otherwise for bitrates ~128k or higher, use the interna

I haven't done or seen any tests, but I suppose if you require VBR and/or HE-AAC support, go for libfdk, otherwise for bitrates ~128k or higher, use the internal AAC encoder.