Well they all send you free books, in the hope you'll pick their one.
Truth be told, in my field the intro level textbooks are essentially indistinguishable, down to graphics and specific examples, and every publisher has one. Even if I got free samples for all of them (I don't), there is zero difference for the student. You look at the classics, maybe check out a new book, but in the end pick the one you're already familiar with because you don't have any time to waste.
But yeah, you won't get rich, but you will get a full bookshelf, so you'll be rich in knowledge ;)