This does seem like a continuation of the other thread. Though on this question, it is hard to answer, as it's a lot like asking whether we prefer cats, roses or bread. Those companies all do different things, and they each have their own competitors. They don't really compete with each other.
Your categories here are...
POD/Print books: Lulu and CreateSpace are the big ones. CreateSpace is generally cheaper (in terms of the price customers pay for the book). Lulu does some other formats, like hardbacks. You're not tied to a particularly company, so if you need hardbacks, you could use Lulu for those and print paperbacks with CreateSpace.
Service to send out books to places: Smashwords and D2D. Note these take a percentage of each sale, but you have full control over book setup and there are no fees for that. You can update your book when you want, remove/add it to sales channels at will, and basically you're in charge.
Service that uploads the book for a fee, often as part of a bigger package with formatting, etc.: Places like Ebookit. Not a good idea for self-publishing. It might look on the surface as though it'll save time and money, but what it really does is remove your control. Only they can update your book, for example. So you have to pay them even for tiny changes. Ultimately, you'll end up paying more by going through this route.
