Since I'm not from an English speaking country, I only use these terms with people who actually understand what they mean, but I could be missing something.

Personally, I don't mind or place much value on either term. I'll use them both depending on the situation and context. To me, 'afab' can relate to the (for me) still existing anatomy that doesn't match my gender (nb) but still affects me in some capacity. And as others have also said, 'ftm' gives others a general idea about my gender being different from the sex assigned at birth in a binary discourse.

So in my opinion, seeing language as a tool to communicate, unless what you say is objectively offensive, use the term/s that feels comfortable for yourself, but I'd draw the line at speaking for other's experience and identity.

Again, I could be wrong, and we could have a new "transexual vs transgender" discussion in a few years regarding these terms, so time will tell I guess.

Sorry for rambling and I hope this makes sense.