If you're going to sell it, or potentially use it as a decoration out in the public eye I'd recommend getting it graded. The Slab will protect the book from harm if some heathen pulls it off the wall to look more closely at better than another other protective item I've encountered.
Selling it, the benefit is that an impartial third party has provided a number, for better or worse. There is no bickering or hesitation on the part of bidders who are staring with bifocals at their shitty monitor wondering if that tiny spec is on the bag or the book.
If you consider grading - I would also suggest a press/clean job (not that expensive, $15 up here), even if the book looks brand new. That one, non-color breaking spine ding can drop you to a 9.2 or 9.4, and might mean $100 or more off the sale price. Fools will pay so much more for 9.6s and 9.8s.
Catchiest Catch Phrase 2008Pork Cutlet! Pork Cutlet will know.... the truuuuuth......