[different_base]

Using OnlyOffice promotes Microsoft Document format even further. Microsoft will again change their spec and OnlyOffice won't know how to render it correctly.

For long term, it's better to choose LibreOffice which uses open standards and does not purposefully change specs to break others.

[extraduder_ire]

Does it not have support for odt? I haven't used it much, but I do generally prefer it to libreoffice if I need to create or edit a document nowadays.

[throwaway74354]

It doesn't have a file creation dialog (nor global setting for this behavior), hence "promotes". New files are docx/xlsx/pptx. You have to manually use a "Save as" dialog to choose a corresponding LibreOffice format.