AVI is currently not supported by IOS and videos do not play for field members that rely on Ipad or Iphone. Exporting in MOV or MP4 would save alot of time re-rendering the video in another software into another format.
Animations can now be exported to mp4 format in SYNCHRO 4D Pro 6.4 released in June 2021
Full 6.4 release notes are here
