The peel or no peel debate has been waging since the inception of the protective coating. One unknown factor has been that of the long-term effects of leaving the peel on. These coatings were never intended to remain on the cards long-term and only time will tell how well they will hold up, whether the cards are professionally graded and sealed or 'raw'.
In terms of the grading of such cards by BGS, it is impossible to grade the surface beneath the coating. Thus, the coating itself must be treated as the surface and graded accordingly. Because these coatings are sometimes scratched, bubbled, or flared, unpeeled cards usually receive lower surface grades than peeled cards. On the other hand, graded non-peeled cards typically command premium values over peeled cards in the same condition.