In my experience, OOXML files don't work well on LibreOffice, probably
because of those things MB mentioned. Everything always seems to render
differently between MS Office and LibreOffice.
I actually remember the whole controversy back when I was in school. My dad
was a vocal critic of OOXML and its standardization. One thing I recall is
that Microsoft Office at that time had no support at all for ODF, and wanting
their office suite to be "standard" without adding support for the already
standard ODF seemed to be a major motivation for pushing through OOXML as a
redundant standard. It was only years later that they finally added ODF
support as an add-on for... Microsoft Office 2010? I think that was it.
Microsoft Office supports ODF now, so that's good. It also means there's no
longer any reason whatsoever to use either the proprietary MS formats, or
OOXML.
h.264, on the other hand, is unfortunately more widely supported than WebM,
and even has a lot of hardware-level support whereas WebM doesn't (meaning a
lot of GPUs can help render h.264 video more smoothly). So unfortunately, it
seems there's going to be a reason to use MP4 for years to come. Maybe VP9
can get as much as or more traction than h.265. One can hope.
