I think Helix has been discussed before on here, but I think I'll give it a review. I purchased a Helix and returned it after 10 days, having spent most of my vacation week playing with it all day. Initially I thought it might simplify things for me live. I'm one of the minority that find the head/remote combo awkward for my uses and would much prefer and all in one floor system, hence why I tried out the Helix. I also thought having a full-featured editor would be a big time saver. But I found several key weaknesses that the Kemper solves.
1) Autovolume matching. Ever notice on the Kemper that the volume is always consistent unless you don't want it to be? Try adjusting gain on the Helix and you're saving, comparing to a base preset, going back adjusting, saving, etc.. Total pain and makes preset management a total pain. Not a unique problem to the Helix, but the definitional problem of every multi-effect/modeling digital preset-based product ever produced.
2) Kemper's fast rig change. Notice that the gap between Rigs on the Kemper is instanenous, like switching channels on a real amp, and has nice spillover? Not so on the Helix. The gap is so big and noticeable with no spillover that it's useless whenever you need to change without a break in playing. Helix tries to solve this by giving you more options to turn things on and off without leaving the preset (snapshots). These are quite convenient, but also come with an annoying complexity. To avoid having to change presets mid song (to avoid the glitch) you have to make ridiculously complex presets with snapshots. Heaven forbid you do something like add a gain increase for the amp block with a switch and decide later you need to raise and lower it a bit. Now all your snapshots are screwed up, at least in regard to that, so now you have to go back and forth and hit all the snapshots, engage and disengage the gain stomp and finally hit save. Granted, if your needs aren't too complex, you might only need a single Preset for a set of songs, in which case the spillover issue would be a non issue.
3) Locking blocks and saving effect presets. the ability on the Kemper to save presets be they single effects, the stack, or the entire stomps or effects section means you can recall this easily in a new rig. You can also lock a block you want to copy onto a ton of different rigs and make therefore make the same changes fairly quickly. On the Helix you can only copy and paste single blocks. So if you built a complex web of delay/reverbs in one preset on the Helix and want to copy them to another, you must go back and forth a dozen times. Thus the open architecture of the Helix in terms of routing makes a huge headache if you want to use the same things in many different presets.
4) Kemper ducking and mix level. So many of the Kemper effects have mix controls and ducking abilities. I can set a nice hall reverb and use a ducking feature in the Kemper so that it goes away some when I strum out and reverberates more when I play single notes or let chords ring out, or arpeggiate. So I avoid having to turn the reverb on and off and/or don't have to compromise with chords that are too mushy and single notes and arpeggios that are too dry. The ducking feature alone makes the built in effects and even external effects much more useful because you can duck them.
5) Helix is capable of good amp sounds, especially if you get some really good IR's to replace the built in cabs. But Kemper still wins in this category.
6) Effects: Kemper's delays and pitch effects are better than what's in the Helix. Helix had more options in overdrive pedals. But given the number of profiles available with baked in OD pedals the advantage is diminished.
In short, the only thing I liked more about the Helix was the ability to be an audio interface, being all-in-one, effects loops which I don't currently need, nice visual display, and the editor. However, I found that even with an editor, the Helix would long-term be a more time consuming product to tweak and keep the sounds I need organized. For a guy that only needs a half a dozen basic tones, but likes to use various combinations of other effects, sometimes subtle and sometimes not so subtle, for 50+ and growing songs, the Kemper is a much simpler way to stay organized and saves time even without an editor.