The paperbacks are usually released several months after the hardcovers so it depends if you mind waiting. I think I'd just go with the paperbacks if you haven't read any yet and want to catch up. They're cheap and take up less space too.
I buy the hardcovers as I've always preferred them. Plus I like to read the novels when they're first released. Well, most of them.
That's good advice.
I'm in no rush to buy them as soon as they come out, so getting cheap paperbacks is probably best for me.
Though I would prefer everything in hardback, just looks better imo.