Helix IMO has one huge benifit over Kakoune - inbuilt LSP and treesitter support and sane defaults. It takes the best bits of kakoune and neovim and improves on them both. This gives me an editor with enough IDE like support that I can use it for just about anything. All with only a few lines of config and zero plugins.
This means I don’t need to spend ages trying to configure my editor to work with various languages or working around its archaic defaults. I can just install it, optionally tweak some minor settings (like the theme and turning off auto bracers), install the LSP servers for the languages I need and I can get to coding.
And after years of fiddling with neovim/vim to get it to it behave in a reasonable, but not perfect, manor helix is a breath of free air. I did try kakoune for a very short time after getting pissed off with neovims configuration and plugins, but gave up on it quickly when I had to dive into getting more plugins configured for even basic things like LSP support (though this was years ago, back when helix was not in a daily usable state either).
Yeah, it would be nice to have plugins in helix (and they will come one day), but IMO the saner defaults and unbuilt support for most of what I used plugins for before is far nicer than getting support for the few bits that might be missing.
Kakoune promotes the idea that you should visually see the text you’re operating on before running the command.
This is what helix does as well, and it shares kakounes keybindings and input system. So it is more similar to kakoune in that regard than vim with different keybindings. Really it is more of a kakoune clone, with inbuilt support for LSP and treesitter like neovim.
For example, instead of it having a built-in sort command, you use the unix sort command to sort your lines.
You can do this in vim and helix as well. Both can run external commands, pipe your open file to external commands or just your current selection to them. I use the unix sort in helix to sort lines all the time.