I happen to own both. I should also start by saying that I have owned the atlas for quite some time at this point and it has been my favorite IEM (also was my most expensive and highest end one).
Right now I am listening to the andromeda gold mostly, maybe because of new toy syndrome, but its also just a very very enjoyable listen, and I think it just happens to take a bit of an edge over the atlas in a lot of areas.
Aside from their obvious sound signature differences (atlas is kind of w with a huge bass emphasis) where andromeda gold is a bit more towards balanced with a bit of a bass boost.Other than that, I would say the andromeda does a better job with microdetails and clarity, though not by a large margin, and andromeda wins in terms of imaging and soundstage. Atlas definitely wins on bass, both in terms of quantity and quality. It has that nice dynamic driver bass that you can almost feel, while the andromeda definitely doesnt lack in bass, but its ba bass, so maybe a bit rolled off in the subbass.
So to sum up, Atlas for a big fun bassy sound, andromeda for a smoother, maybe slightly more detailed, yet still fun sound with great soundstage.