I was actually really excited to see this question! Of course, the old mantra "Don't judge a book by it's cover" comes to mind, as well as the shameful admission that "I do, I do!" Because really, who doesn't? Yeah, usually we read books because of their merit or what we've heard about them or because some teacher makes up, but sometimes we find ourselves wandering around the bookstore just looking for something new. And how the hell are we supposed to find something new unless we pick up something randomly and what's going to inspire us to pick up something randomly unless it has an appealing cover? Even when we know what we're looking for, it's not a rare occurrence to choose an edition based on which has the nicer cover. For example, which edition of Tess of the D'Urbervilles would you choose?
Sure, you might choose the Oxford World's Classics edition because they're known for having really excellent footnotes and whatnot but in terms of aesthetics, if you're anything like me you'll be choosing the Broadview Press edition. The Oxford cover is kind of washed out and boring to look at, with an obnoxious bright red interruption to the image, while the Broadview cover has the lovely contrast of black and white and keeps the focus on the girl, rather than some cow. The cover information doesn't make such a stark contrast and, though you can't tell from the picture, the book is a pleasure to hold. It's satiny smooth and of the perfect weight: substantial, but not to heavy to carry around. So nice.
Though it may not be completely true as I don't have all my books in front of me (they mostly live at my parents' house), I think that Broadview covers are my favorite. I was required to buy a bunch of them for my beloved Victorian fiction class and I just loved them. My then-fiance and then-roommate thought I was absolutely insane because I kept pulling them out of the bag and showing them off.
The two tones are beautiful and the really stark images, that don't fade away into background, are just so beautiful to me. However, in the interest of full disclosure, the helpfulness of the footnotes in these books can be consistent and they are fraught with editorial errors. They're so nice to hold and look at though that I forgive them.