I’d like to know how many supported file formats LibreOffice has, and if someone knows, how does this compare to Office 2013 and Office 365?
For 5.x:
what-are-the-5x-writer-importexport-filters
For 6.x:
what-are-the-6x-writer-importexport-filters
In a couple of words: lots & lots!
I do not know the exact number but this recent blog post gives a decent account and indicates that LO supports more formats than the current versions of MSO.