I much prefer to purchase slabbed books online now, because in my experience sellers often tend to overstate grade and I end up disappointed with what I receive. Even then it's not usually worth the hassle to return it and eat the shipping charges so I'm stuck with it. I usually only purchase raw if it's one I want for my personal collection in any grade or I'm willing to gamble on a low-cost book. Books graded "NM" seem particularly notorious for overgrading, as I've received them with defects ranging from several color-breaking creases to ripped or missing interior pages and water damage.
From a buyer's perspective, I want sellers to provide an estimated grade and several pictures. This gives a starting point and lets me decide from there. If I'm looking for 9.0 it saves the time reading through a 4.0 listing. An estimated grade gives a good starting point to review photos and decide for myself. Without an estimated grade there's no reference from the person who can see it in person. From there, sellers should include front and back photos at a minimum. A single fuzzy cover shot through a dingy bag with the bottom edge cut off in the photo doesn't cut it.