I bought both blind at the same time and frankly I think the amiron is one of the worst sounding headphones I’ve owned. I sold it within a few weeks. The midrange is far too recessed and the weird hump in the lower mids sounds extremely wooly and muddy to me. The DT1990 is much better in this regard but still has a fair bit of it going on.
To be honest the DT 900 pro x blows them both out of the water for less money and I think the DT 900 pretty much obsoletes both the 1990 and amiron.
IEMs are literally just about getting a tuning that works for you.