Yes, there is a huge difference, and you hit the nail on the head regarding why supermarket cooking wine is terrible. It contains a massive amount of added salt and preservatives to prevent it from spoiling on the shelf, which is why it tastes like salty ocean water. You should definitely avoid it. Instead, buy a cheap bottle of drinkable wine, like a simple five-dollar pinot grigio or merlot. It will make your food taste infinitely better, add actual depth of flavor, and you can even enjoy a glass with your meal prep.