I used the Wilbur/Graber book to study OB/GYn, biostat, and parts of PEDs and mostly liked the book. I wanted to kick myself in the butt for pulling it off the shelf too late in my Step 3 prep (only 5 days before the exam). I mostly did qbank questions for prep.
I bought the book in medical school from a local med book store run by a family who were impressively knowledgeable on every book they sold. They knew much about the book from feedback from all of the students and residents who gave them feedback over the years. I loved those guys because even though they were running a business, they gave unbiased feedback on all of their products. When I bought the book, they really gave it a very enthusiastic recommendation and told me that I would be "very prepared to take Step 3 when I bought it." While reading the above mentioned chapters, I felt that I was learning a lot and liked the format of their step-by-step questions. They even incorporate a bit of humor. However, one thing that really bugged me about the book is that the occasionally made up answers and would even joke about making up the answer in the explanations. I really hate made up answers for questions especially since it does not represent the exam design that they are supposeddly preparing you for.
In short, although I am unfamiliar with Swanson's, I would still recommend this Wilbur/Graber book as a supplement to another prep book such as Crush Step 3 which I hear is good but is skimpy in areas such as OB/GYN which, of course, is a significant part of Step 3. I hope that helps. Good luck!