I’ve used a lot of headphones and a lot of earbuds. I don’t know where the other two responses came from, seem to be duplicates on some level. But I can tell you that KZ earbuds are quite different from the usual offerings from Sony and other big brands and offer better value than the vast majority of earbuds.
In terms of overall balance, most reviews I’ve read favor the KZ ATE. What I’ve heard is one of the few earbuds that can reproduce acoustic music without too much distress—it’s amazing how many headphones and earbuds cannot adequately reproduce massed strings, and by “adequate” I mean not burn your ears off or throw a wet blanket over the strings.
The $15 KZ ATE earbuds I got last week are better than the Beyerdynamic earbuds I got a month ago that were discounted from $100 to $30, better than the $30 extra-bass Sonys I got a year ago, way better than the Sols I bought at a deep discount but still pricier than the KZ ATEs.
The ATEs are smooth in the upper octaves, and powerful in the lower octaves as the ZSTs. Of all the ZK ATEs are at around $15.