MOV or MP4 for Youtube ?

The typical reason for choosing MP4 over MOV is wider compatibility. That doesn't apply when uploading to YT since they'll recompress the file and make multiple versions for different devices.

As you mention, the two extensions denote different (but closely-related) containers. The quality should not be affected by the choice, assuming comparable compressions.

Good luck.

Russ

I find ProRes files get better results than MP4.

There's been a lot of news lately about Apple discontinuing Quicktime support for PCs. I'm concerned that if I generate YouTube MOV files for clients who may be on a PC, it may cause them problems.