how similar are Sibelius's and MuseScore's MusicXML files?

I'm interested in how similarly Sibelius and MuseScore generate MusicXML files.

The reason is that I worked with Sibelius for many years and wrote some custom software that reads its MusicXML output in order to provide custom playback through samplers and Pianoteq with expression added. I paid something like $600 for a perpetual license a number of years ago. Well that version of Sibelius is now broken with MacOS Big Sur. I don't feel like switching to an expensive subscription model to get the latest version. MuseScore sounds better.

Working with MusicXML I discovered that there's not really a core standard for how music is represented. Given a piece of music by looking at its printed score, you have options about how you translate that into MusicXML.

If I switch to MuseScore I'd like my software to keep working, but this depends on the idea that Sibelius and MuseScore output are similar.

So if anyone knows this, comments appreciated. If you haven't looked at the internals of MusicXML you can still probably get a feel for how well MusicXML exports from one program become imports for the other program -- I mean how similar the scores look.

thanks,
Mike