The big advantage of flats for most people is the gain in confidence when learning new stuff, around 50% of the people I train who arrive clipped in leave on flats. However, if you've always run clips and go to flats the feeling of not being quite as connected to the bike could have the opposite effect.
Good technique is good technique regardless of pedals but there is an argument that clips may allow you to be a little sloppy with certain aspects … so if you can master stuff on flats it will transfer over when you're clipped in but perhaps not always the other wat round.
BTW I run flats and consider clips to be the work of the devil so perhaps I'm a little biased 😉
Stuart