When my business partner and I co-founded our business, we set out to try and be as open-source as possible, beyond a few things that were required due to what we do. One of the big areas was Microsoft Office compatibility. Our team tested our heaviest word documents from clients, which include government, banking, and lawyers. The least issues we had were with OnlyOffice out of it, LibreOffice, and Softmaker. Due to those same clients, we were unable to use WPSOffice. On the Excel side was more problematic and pretty equal between the 3 tested.
We do also have Office 365 for business due to a few compliances we have to comply with, but we rarely use any of the actual Office apps, other than in rare cases.
That said, my favorite project is easily LibreOffice and it actually works quite well for most things.