If the writing does not get me involved, I have quit long before any plot has been revealed. I am one of those evil people who can and do drop a book in the first chapter. No guilt and no apologies because my reading time matters to me.
I'm jut saying that I think hype generally will sell a book faster than its inherent qualities. I don't think there's any way to determine which will sell faster between the choices Jude gave. But I'm not in marketing either, so.
I agree about Chandler's plots -- in THE BIG SLEEP, one murder is never explained at all -- but I think he was one heck of a storyteller, meaning he had the reader (me, anyway) gripped. I had to keep turning pages, had to find out what happened to Marlowe next. I believe this is the essential need of all storytelling, from the first campfire to today's bestsellers, although of course there are many exceptions. Fame, platform, and previous good works bring all sorts of novels to the bestseller list.
I am afraid you are right! - which is so unfair :(
And I must admit that I read some crime novels which are poorly written if the plot is catching but I would never review it as positively as the well written books and I rarely buy books of this category.
Perhaps because I write, I'm notoriously impatient with poor writing. I also notice that frequently I seem to be the only one. Just tossed Michael Grigorio's CRITIQUE OF CRIMINAL REASON for poor writing (and careless historical background). I seem to remember getting the book (in the library, fortunately) because it was extravagantly praised somewhere (someone's best of 2008 ?). The book is the author's first and very badly overwritten stylistically. He is a philosophy professor, so I expect thematically (the serial killer thriller turns on Kant's philosophy) is probably fine. The plot may also be okay. I just didn't get far enough in to find out. (Have no time to waste on bad books)