Unless the original art was really tacky, I'd prefer the original art. There are several used books selling for more than a hundred dollars, out there, even though the newer versions are inexpensive, and I think it's partially because the older art was so iconic or at least loved.

I prefer paperbacks of the "pocket book" size, though of course I would prefer they be well-made and durable even though I'll be gentle with them. I like to be able to hold and read the book with one hand, if it's possible.

If I have a hardback, I feel like I have even more of a responsibility to "rehome it responsibly" and if it doesn't have the dust jacket, it's harder to do that. But other than that, the dust jacket is almost an annoyance; they're so fragile!

Most important of all, though; if the book is of a series? It should not vary drastically in shape or appearance from the others. I was more than a little frustrated when I owned the three (extremely good) Barry Hughart books but one was an inch taller and a half inch longer than the other two. Frustrating. But, alas, his stuff isn't as well known as it deserves.