Printers For Self-Publishers

One of the basic derogatory terms by some self-publishers is to call every publisher who asks for money a "vanity press." The idea is that since you are paying them to publish, it's just another worthless scammer; you should never have to pay to publish. This only applies to traditional publishers. The reality is that unless you're working with a traditional publisher most people are going to need to pay someone to be published; not everyone has all of the skills needed to be a successful self-publisher, after all. However, it may not be a bad idea to go through the various types of printers and publishers out there and how they work when it comes to self-publishing to get a better idea of what's available.

Vanity Press

These presses pretty much just print books. They have a bad reputation because too many of them took advantage of new authors, although there are some legitimate vanity presses. Currently, they are used by clients for specific, usually one-shot, projects. 

Usefulness: None. They are the most expensive option, offer limited distribution options (usually just a listing on their site), and generally don't offer editorial services (although they may offer them through third-party vendors).

Offset Presses

By using a system of films, these presses can create high-quality books with beautiful pictures. While there is usually a set-up cost, it's a one-time cost (it only needs to be paid again if there are changes to the content). 

Usefulness: While they don't offer editorial services, they do offer discounts based on the number of books printed. Note that this does result in a physical product that needs to be stored, packaged, and shipped out by hand. Shipping also needs to be considered, as the shipping costs may be more than expected (so look for a local press or really debate foreign ones).

Print On Demand (POD)

POD printers are so-called because they only print books (and other merchandise) when asked for by customers. This means that the author doesn't need to worry about keeping an inventory or dealing with fulfillment issues, and saves a lot on upfront costs. The author just needs to upload the files and market the link. 

Usefulness: The author doesn't need to pay for printing so that eliminates a major cost for self-publishers. Some of these sites offer access to other merchandise, so the author can create salable merchandise such as T-shirts, posters, and bookmarks. Most of these sites have limited distribution, so look at them carefully.

Hybrid Publishers/Author Services Sites 

These mix the services available from traditional publishers but a la carte, so self-publishers can decide which services they actually need, or at least are willing to pay for. Make sure you look for signs that the publisher is following the Independent Book Publishers Association criteria, eleven points that ensure the hybrid publisher isn't just a scam (some have even started calling themselves "author service sites" to differentiate themselves from scammers). 

Usefulness: These act as one-stop shops for self-publishers as they have the full range of services, sometimes even including distribution. However, they do need to be carefully vetted and price comparisons aren't a bad idea.

Platforms

These are essentially POD sites with extensive distribution networks, like Amazon. While some do have access to other options, such as brick-and-mortar stores, they tend to focus on getting their books to as many different areas as possible. 

Usefulness: For authors looking to solve distribution issues, these are pretty good. While they usually only offer editorial services through third-party vendors, those vendors are pretty well vetted. Also, some focus on ebooks alone. It should be noted that Amazon does have a fulfillment center so that an author could print their books elsewhere and still have it deal with storage and fulfillment issues, but it is a paid service and ignores the POD aspect.

Aggregators

These POD sites offer self-publishers to put their books on as many sites as possible. While it is advised to focus on sites when possible (for example, while Barnes & Nobles is served by Draft2Digital, there are some advantages to loading a book directly to Barnes & Nobles). 

Usefulness: These ensure an incredibly wide distribution net with little work. While printing options are limited, this is still a great way to get your book out there.

Traditional Publishers

This applies to any publisher who is actually in the business of publishing books and pays its authors to do so. While you lose some control and the royalties per book are smaller, you're more likely to sell books and you pay a lot less to print. The standards are also higher to get published, and you usually need to deal with an agent. 

Usefulness: All of your editorial costs are taken care of and most of your marketing is taken care of. You will lose some control over the process, but you're also more likely to make money.

Scammers

While these purport to be one or more of the above, they are usually there just to steal money and/or copyrights from unsuspecting authors. This is why you need to vet anyone you seek to do business with. Using things like Facebook groups is debatable, however, as some group members have had bad experiences with some publishers or are going by third-hand information, and so they call perfectly legitimate publishers "scammers." This is why you need to vet them on your own. Looking at the contract also helps: If you lose any more rights than those needed to print the book (especially copyrights), RUN. 

Usefulness: None, unless you're looking to lose time and money for no effect and possibly even lose your rights.

So, which printer is best for you? It's completely up to you. Some authors don't limit themselves to just one option because it just doesn't make sense to them: They may use a hybrid publisher to create the book, put their books up on a platform or two, and then use an aggregator to cover a lot more territory; others will pay or do all of the work themselves and then put the book up on a platform. There is no one-size-fits-all plan, except to avoid vanity presses and scammers. See what works for you and good luck!