The Custom Art ME are probably closer to the Legend X in signature. The Legend X is technically more proficient than the ME, and the Atlas truly succeeds at what is designed and tune to do. The Atlas is hellaciously addictive and engaging. It receives a lot of ear time these days, although I should be listening critically to other IEMs that I need to review first. Quick impressions dont tell the story of this IEM, and really don't do it justice.
Agreed with the part where you say quick impressions don't do justice to the Atlas. What I mean by Legend X + Atlas similarities is they both give me that engaging, emotional and immersive feel. They really draw me into the music vs. "thinking" about it (ex: IEMs that are more reference like where you focus on placement, accuracy, separation and layering). They can do it without sounding like a pile of mush. I'm basically bobbing my head when listening to them.
On a side note, the Atlas passes my subway/supermarket/crowded streets daily test. I commute about 1.5 hours a day by public transit. Bass and especially sub-bass is the first thing you lose with poor isolation and thanks to the sub-bass bump of the Atlas, I can still hear plenty of it while still out and about.