First, as mentioned, AS10 is quite source dependent with its low impedance. Also quite particularly so, with more bass from a lower power source, as smartphone, and much tighter bass being powered for instance with a capable balanced source. I personally quite liked AS10 with a smartphone and sometimes relive this experience, but typically use it balanced.
Then sufficiently powered from the same source, AS12 has more bass to my ears (and 2 out of 6 vs. 1 out of 5 is an attempt on math support of it).
After liking AS12 initially, I found its timbre a bit constrained to my ears and removed its treble filters (made it quite bright even sibilant, which is a different story...)
Related actually, the only other successor of AS10, I can think of, is CCA A10 (5 BAs). A10 to me is a logical development to expand the treble (works for me) but is generally perceived as "too bright".
So overall, AS10 happened to be truly unique, especially with its interesting source dependence.
It seems hard to add more bass and expanding the treble rather makes an entirely different IEM.
So I just enjoy its uniqueness, and just in case got a second copy and BA10 (same driver in an acoustically superior and nicely made but gigantic shell).
That is my limited take on it.
