

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.
In my early teens, I got really into computers, built my first PC when I was about 13, started learning Windows batch scripting and using GameMaker to make goofy PC games.
Along the way, I found Trinity Rescue Kit and was also introduced to Fedora Core by a nerdy guy who worked at my local YMCA.
I didn’t actually enjoy it too much back then, so I left it alone for years until about 5 years ago when I started to get back into the free software movement and related interests.
I’ve been 100% on Linux for about 4 years now and never looked back.