I think the badly written one - I'm currently reading a book like that, and it's killing me. I'm interested in what happens next, so I can't stop reading it, but when reading conversations, I'm constantly thinking, "No one would ever talk like that!". Also, I have to reread many sentences, because the wording is so bad that the sentences don't make sense. Plus, the names are all SO hokey, like soap opera names. But I HAVE to know why Lily's Explorer went off the road!
And, while writing this question, I realized it can be translated to movies, too, so - which is better on the big screen? A boring movie with no real direction, but that has excellent acting and a good script; or a film with a good idea, but hams for the lead roles and bad camera work? (Not necessarily those problems, but just an overall "bad B movie"?)