I have found quite a difference in food grade and cosmetic grade.
Food grade is usually more expensive.
Food grade oftentimes means that you can also eat the product. Not all the time, depends on what the oil is; for ex: food grade Lye is NOT edible.
Food grade is usually unrefined and it is quite evident just by looking at the product. I usually prefer food grade oils.
Cosmetic grade is strictly for products. It is not edible Cosmetic grade is usually refined and less expensive.
Anyone else want to chime in?