All other things being equal–do you prefer used books? Or new books? (The physical speciman, that is, not the title.) Does your preference differentiate between a standard kind of used book, and a pristine, leather-bound copy?
If I buy a book, I prefer a new copy. I like the scent of freshly printed pages and the feeling that a book is only mine. Plus, buying new hard copies helps printed books survive in the electronic era.