When comparing ButterCMS vs Squidex, the Slant community recommends ButterCMS for most people. In the question“What are the best open source headless CMS's?” ButterCMS is ranked 13th while Squidex is ranked 17th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Integrate with any language/framework
Pro Open source
Pro Versioning
Pro Powerful rule engine for integrations
Pro REST and GraphQL
Pro Slick UI
Pro Generous free package
2 locales, 2 collaborators, many API calls
Cons
Con Not really open-source
Although API and SDK's are available on GitHub, the CMS source code is not.
Con Limited to SImple Content
Limited to simple displaying of contents but will struggle with complex business rules ie ones that require cascading drop-downs, complex nested documents, etc..
Con Un-debuggable Script Editors
You can't debug any of its in-built script editors
Con References
It will allow you to delete references which are used by documents and when you come to open those documents, it will then perform its 'shake' logic to remove it (make it balnk') and will also disappear from history / versioning