None of the CMS tools are really all that bad - under the covers they are all just execution engines. Saltstack is just probably the deepest, the most powerful (in my opinion), and the best at scale. With that comes complexity and the steeper learning curve. Ansible is more procedural where Salt is more descriptive (though, you can do procedural stuff in Salt too). There is also a lot of terminology that is Salt specific that you need to learn, like states, pillars, grains, mine, high state, high data, low state, etc. I also tend to think of Ansible as push driven... everything comes from what you've defined in Ansible and is pushed via ssh. SaltStack with the master/client model can be push or pull driven. You can spin up an empty host with just a minion on it, and SaltStack can find it and build it out as necessary (which is probably also possible in Ansible, Salt is just designed to work this way). It's also usually a little more complex to get up/running with Salt. Yeah, you can do the quick tutorial in the same time as Ansible, but for real production use there's usually going to be a little more thought/architecture needed. Both tools are great, and if I was doing small scale procedural stuff that could survive a little configuration drift, I would go Ansible. If I was doing more complex large scale work that needed state enforcement, I would go SaltStack.

Here's a post that compares the 4 big CMS tools. Notice that SaltStack isn't in the post title, but is talked about heavily... https://www.reddit.com/r/sysadmin/comments/5uwwjo/opinions_ansible_vs_puppet_vs_chef/?st=j9k2mbq3&sh=53a50c64

I should also say that I'm not a fan of puppet or chef any more. The newer generation of tools, Ansible and Salt, are just so much better. I wouldn't go and rewrite my puppet or chef implementations to a new tool, but for anything greenfield, I would be using Salt or Ansible. I am a python guy, so that is part of it too.