Same here Daniel; talked with some production guys at Disney, Joe Kane questions, and some other less notiable sources - all say the end results with VC1 and MPEG4 are very close in quality (each better than the other for certain scenes), but the AV1 tool set is more developed.

Recently, some posts from professional encoders though have noted the newest MPEG4 tool set doing a lot catchup; Msoft did a great job with AV1 development apparently, but having 2 good ones around is always good I think...