I wouldn't expect there would be a dif between FLAC and Apple Lossless (I assume that's ALAC?). By definition, they're both lossless. Didn't we have this discussion in another thread?
There probably was a discussion but I think I stayed away from that one. I've been re-ripping to ALAC because I've got back into head-fi and I have a few headphone amps I'm testing out to see which one I'll keep. I'm using Grado 325i's, waiting for a limited edition Grado to be shipped.
I'm w/ you, not sure if I would be able to tell the difference between FLAC and ALAC. But I can guarantee you, there are folks on head-fi.org that'll claim that they can. Maybe they can, maybe they can't. Who knows. I know that I can't. I tried to A/B a 320 Kbps MP3 and the same song ripped to FLAC. Could I tell the difference? I 'think' I could but it was so minor that if I wasn't paying attention, I probably wouldn't notice. But my iPhone notices, because the files are sometimes 3x the size.