I think it's:
ATR: Newest on the AT line. Quite inexpensive but most prefer it for a more balanced sound over the ATE/ATES
ATES: ATE with memory wire
Still waiting on my Piston Youth editions. I do have the Piston 3, Piston Basic, and Piston Colorfuls. All are a bit less bassy than the ATR.
In terms of bass: ATR>Piston3>Piston Basic>Piston Colorful.
To be honest though, all are pretty good IEMs, especially for the price($5-$10 lmao, buy a truckload and never worry about breaking them again).
In terms of fit and finish, I like the colorful the best. Nice flat cable, thick rubber strain reliefs, super lightweight. Fit is great.
Soundwise I like the ATR. Bass is a lot punchier and fuller, and the highs aren't as fatiguing on the ears. Cable is a bit springy and tangle prone, and the fit is not as good nor as easy to insert as the Piston lineup.
I think the Piston 3 would be the best compromise between all of the IEMs I have, but sadly they're discontinued and also were a bit more expensive than the ATR and Colorful and Basic.