It’s designed to be more compatible with MS’ .docx formats, less weird formatting issues when converting between them. But the actual features it has is less than LibreOffice.
Two different focuses, LibreOffice is designed with more powerful features and uses the .odf file format by default.
OnlyOffice is lighter weight and designed with MS Office compatibility first and foremost, although both suites support both file formats and in my experience, both work great with either file types and for basic users, have all the features you would need.
It’s designed to be more compatible with MS’ .docx formats, less weird formatting issues when converting between them. But the actual features it has is less than LibreOffice.
Two different focuses, LibreOffice is designed with more powerful features and uses the .odf file format by default.
OnlyOffice is lighter weight and designed with MS Office compatibility first and foremost, although both suites support both file formats and in my experience, both work great with either file types and for basic users, have all the features you would need.