Only you can answer this question, but here are two basic considerations you should include in the metrics:

1. Do you have a full understanding of what various levels of credit signify?

• WITH is typically employed after the Author’s name on the cover and other references to the title. The reader will find the Author’s name in bigger, bolder print, and below it, smaller, the ghost’s credit, e.g.:

My Life and Times with Martha
By George Washington
With Thadeus Chapcranter III

• WITH usually signifies a ghost’s involvement in writing, organizing, editing, and clarifying the message—but reminds the reader that the message originates and remains with the Author. The Author’s material, the Writer’s (Ghost’s) words.

• AND is more often than not a signal that both parties originated, developed, and contributed to the material, though not necessarily in equal measure. Though you’ll typically see both names in the same size type on either side of the AND, the principal contributor/originator will come first, e.g.:

Cherry Trees, Wooden Teeth, & Other Myths of My Life
By George Washington
And Heronymus Bumblepuppy

• AS TOLD TO, becoming less common of late, but still applicable with certain celebrity memoirs, etc. It connotes – but doesn’t exactly denote – that the ghost merely “transcribed” the material of the Author, possibly doing some “light” editing or even some level of book-doctoring. Typically, the ghost in reality will have performed the same level of writing, but an Author might wish to downplay the ghost’s involvement. Having said that, everyone in publishing – and many savvy readers – will understand the ghost played a major role.

• NO CREDIT. All ghostwriters ought to express a willingness to go this route. It’s not about the ghost—but the Author.  But Authors shouldn’t be surprised if uncredited ghosts ask for an increase in fees. In all cases, the ghost should retain the right to use the book on his or her CV and other self-promotion within the industry.

2.  Do you think the transparent acknowledgment of the ghost will hamper – or help – the marketing of the book and the furtherance of your mission? For example, if you’re a Classics Professor from Oxford, readers might wonder why you needed a ghost for a book about St. Augustine. But if you’re a famous hockey goalie, readers might wonder (possibly unfairly) whether you’re capable of writing a good book without assistance from a professional. Further, if a trusted and tested ghost happens to be involved in your topic, it could help to have the ghost transparently involved in the book, so that you can extend your reach, with both of you promoting, marketing, and selling the book. For example, you’re a renowned ocular surgeon, and your ghost happens to be a former patient whose blindness you cured: You’re not wise to hide this guy under a bushel.