I've found that the Helix tuner works well with one of my guitars but not with another, both work fine with other tuners. Many guitarists have one primary guitar, if the Helix tuner doesn't work well with it they think the tuner is poorly implemented, if the tuner does work for them they wonder what all the fuss is about.
I haven't encountered this with other tuners. The Kemper has an incredible strobe tuner as well as other tuner options. The Kemper is more expensive than the Helix, but that doesn't explain why the Helix tuner can't compete with a $15 Snark.