In my opinion, you should never send a pitch to a publisher if you are expecting them to buy your book and pay you with an advance. Any commercial publisher worth their salt doesn’t accept queries and pitches directly from authors. That is what agents are for.
That being said, if you are looking for a business partner for your publishing, you’re in a different situation. Working with a commercial publisher, they are the boss because they have paid you. Hiring a publisher yourself puts you in the driver’s seat. The model is completely different! This model is for people who have the financial capability of participating in the business of their book and in taking on the risk. They are also the people who know that those who take the risks also benefit from the rewards. The average profit margin for the author in a commercial publishing structure is around $1 per book. Our clients earn 400% to 800% more per book!
So, if you are in the financial position to call the shots, you want to find a publishing company that is going to surround you with an exceptional team, that is going to behave professionally, and whose books and authors you respect. DO YOUR HOMEWORK. Working with companies like createspace and lulu and authorhouse, is a different experience than working with a Writers of the Round Table or a Wyatt McKenzie. The former are companies that provide very little customer service. They make their money from the volume of authors they attract who pay for template services that require no human interaction; not from book sales and elite services. The latter are companies that provide tremendous personal attention and creative teams that focus on both the creative process and the resulting sales.
Compare pricing and revenue models.
Compare customer service practices.
Compare services (template services, vs. original branding).
Compare up-front fees.
Compare the quality of the design and the writing of books they represent.
All of these should be part of your decision making process.