I prefer cooking the chicken breast whole since it allows for a great sear on the outside while keeping the inside juicy. It gets sliced or chopped up after it has had a chance to rest for a few minutes while the veggies cook. Cooking the chicken and veggies separately allows each component to shine and taste their best! The chicken can be seared to perfection and the veggies can be cooked just long enough to still retain some crispness.