What’s so special about sous vide cooking that can’t be done via other cooking methods?
Sous vide cooking is done in a sealed plastic bag, submerged in water, this provides the following advantages:
-precision - exact temperature can achieved to prevent overcooking/undercooking, advantage over oven.
-even cooking - the entire food item is heated evenly on all sides, advantage over grill. 
-moisture retention - the moisture is retained in the food, in the bag, advantage over oven, microwave.
Thank you
Happy to help! Let me know if you need any additional information about sous vide or other cooking methods.