FLV is a relic of the Flash era: the format YouTube grew up on, stranded when Flash died. It was born in 2002, Macromedia (later Adobe), for Flash Player, and its real weak spot is playing anywhere at all since Flash was switched off in 2020.
MOV is Apple's homebody: gorgeous on a Mac, awkward everywhere else. The QuickTime container; often H.264 or HEVC, sometimes heavyweight editing codecs like ProRes. That makes it the right destination when what you need is shooting and editing on Apple hardware, where it's the native tongue.