We live in a world where the most successful in a given field typically possess money, power and influence. For writers trying to make decisions on how to publish consider this: big publishers are in possession of all three. They have more resources, i.e. money, than all of their competitors and they retain the power and influence in a difficult market.
This is not an endorsement of big publishers but merely a fact of the business. Opportunities for success as an author are not equal between larger companies and smaller publishers nor independent and print on demand. Perception is reality in book publishing and the recognition, endorsement and support a big publisher is an advantage but never a guarantee.
Being under contract to a big publishing company results in pressure to write and create content in a timely manner. The ability to manage the process of publication, an editor, marketing and publicity departments can be impossible if the writer does not have a clear understanding of the industry and marketplace.
Depending on the personal and professional goals of the writer a smaller percentage of royalty on a far larger volume of sales plus regional or national exposure may be preferable. Receiving a larger percent of royalty on a small volume of sales may not match the long term goals of the writer. Willingness to share some of the money and control could result in more power and influence over the course of a career.