I'm trying to train my ear, I had 2 teachers before, one of them recommends me to use scale degree in context of the key (which is basically movable do) and the other teacher recommends me fixed do.
I don't think the teacher who uses fixed do has perfect pitch but her ears seems really good. I was playing a piece (which I don't think she's heard before) I played one wrong note and she immediately says shouldn't it be this note?
my other teacher who uses movable do can hear harmonic progression very well. in real time also. but I don't know his ability to transcribe notes in real time.
now I think that movable do is superior because let's face it. fixed do is for the people who has perfect pitch but I'm going to give the benefit of the doubt because she says that you have to use fixed do for a very long time. I think she may have developed semi perfect pitch. like she can only have perfect pitch when it's only on the piano. she cannot reproduce notes or things that people who actually have perfect pitch can do.
while that seems nice but that means I literally have to sing everything I learn in fixed for a long time.
why I think movable do is practical is because well herethis guy explains this perfectly 2:25 for the main point.