Kato is my first and only IEM and I still prefer it to similarly priced and more expensive IEMs I've tried, except one.

IE600: the most technically capable single DD IEM according to some people, but to my ears the bass is too boomy and the treble peak is crazy.

U12T: best all rounder IEMs to some people, but the upper treble just kills it for me.

EXT: lack of upper mid makes the IEM sound unengaging and unnatural

Variations: great mids and treble, but the bass is too much for me

Zen Pro: too much mid bass and upper treble, a bit metallic sounding

Diva: the exception; great tuning and very natural sound with excellent separation. If I want an upgrade, it'll be this IEM.

So, tuning > technicalities all the way for me and since I'm (apparently) very treble sensitive, a nonlinear treble is the biggest and most common deal breaker for me.