What format to publish your book is an essential decision to keep in mind as you choose publishing options. Your decision will depend on two things: impression and price/profit.
Hardbacks connote significance, paperbacks connote practicality
A hardback tells the reader “This is an important book.” Hardbacks are appropriate for serious topics where you want to make an impact, such as big idea books and memoirs. And hardbacks have some visual advantages: you can usually create a dust jacket with graphics and space on the bookflaps for marketing. (Some hardback formats, known as paper-over-board, are more similar to textbooks, with a hard cover and no dust jacket. Writing Without Bullshit is an example.)
Paperbacks communicate “This is useful.” They’re appropriate for practical how-to books. You have more limited space for marketing copy and blurbs: just the back of the book.
Hardbacks cost more and are priced higher
Hardbacks are more expensive to manufacture, and are therefore typically priced at around $30 retail. This also means more profit per unit for the publisher (because of the greater difference between wholesale price and the manufacturing cost) as well as for you, the author (because your royalties are typically a percentage of the list price).
Paperbacks are cheaper to make, and are therefore priced lower (more like $20 than $30, depending on page count). That can boost sales volume, but it means less money per unit for publishers and authors.
How to decide based on your publishing model
Your decision will look different depending on which path you choose to publication.
If you sign a contract with a traditional publisher, the publisher has already decided if your book should be a hardback or a paperback, based on the type of book. You can try to change their minds, but you’ll need a pretty good argument. If a hardback book sells well, the publisher can later bring out a revised edition in paperback, which gives you and them a chance at a second launch and an excuse to win over new readers.
If you are working with a hybrid publisher, you and the publisher will decide on the book format together. Much of the cost of working with a hybrid publisher is printing cost, so publishing in hardback will cost you tens of thousands of dollars more. But you still might decide it’s still the best option, since you’ll make a bigger impression and generate more royalty per unit.
Authors who are self-publishing with print-on-demand technology mostly choose to publish in paperback. While Ingram Spark and Amazon Kindle Direct Publishing are both capable of creating print-on-demand hardbacks, they’re harder to design and have to be priced higher.
If you’re trying to maximize your audience, it makes sense that a lower-priced paperback might be best. But if you want that audience to take you more seriously, a hardback might actually be better — and could even sell more because it seems more substantial. You’ll have to balance those factors as you make your choice.