There isn't any significant difference in quality, but .mov is possibly best option for anything apple.

A lot of older computers will struggle to play 4K without jerkiness, and some only just mange 1080p with high bitrate.
Different players seem to manage better, and updating codecs will sometimes make a big difference  

Possibly the first videos played jekily because the computer was doing something else using resources?
For example if mine is rendering an edited video it can't play another saved clip while you wait