The preface of On Becoming Baby Wise states, "Examine carefully the alternative [parenting] theories, approaches, and specifically observe the end results" (page 17). Here, Gary Ezzo encourages parents to look at different options in raising children and decide what will work best for your family.
First of all, I love that he encourages parents to study different strategies out. He doesn't tell you to blindly believe that what he is saying is the best way for your family. He tells you to look at the different options.
But as a parent, looking at different options gets confusing. Most books are written quite persuasively. You can read one book and say, "Yes! This is the best way!", then read another book--on the opposite end of the spectrum, and say, "No, wait. This is the best way?"
Some will definitely speak to you more than others. For example, for me, attachment parenting in general does not appeal to me. Are there things that are nice? Sure. But it obviously isn't my thing in general. But you can and will find discrepancies even among books that are quite similar foundationally. The Baby Whisperer and Babywise are quite similar on the surface. The major difference between the two is Babywise states that a few minutes of crying won't harm your baby while the Baby Whisperer states that allowing your child to cry in bed alone will break all trust.
Yes, it gets confusing. Some parents create their own plan by choosing different facets from different books and meshing them together. For some, this works out with great results. I have friends like that. For others, things end up a huge mess. I know people like that. I don't know if it is what the parents choose, how they meshed things, the experience of parents coming into parenthood, the baby, etc.
As a sidebar (this isn't the point of this post, but I am sure people will find it of interest), my approach has been to choose one theory and add in things from other books that are harmonious with that theory. If you are familiar with this blog, you see that I have read and continue to read lots of parenting books. I first have my faith that guides me in my parenting. I have Babywise and the following books that I follow. I then take things from other books that I want to add to it. So I have my main course with pot luck from other books.
Okay, back to the point of this post. You are reading different theories and not quite sure what path to embark on. Take note of the italicized parts of the quote. "...observe the end results. " This means you look at the actual products of these theories--the children and families. You look at how these children, parents, and families are. How do the children act? How are the parents? Are they frazzled? How is the family dynamic? How does the marriage relationship seem to be?
Also consider, how does your personality compare to the parent in this other family? Different theories definitely are more compatible with different personalities. That doesn't mean there is only one type in each theory, but you will find more of a certain type in each theory. Consider also how your values compare.
Keep in mind that there is a public face and a private face. Most families look more perfect from the outside than they actually are. People aren't perfect. But a great thing about children is that they only have one face. If anything, they act up more in public than in private. So they are a great resource for deciding what theory you like best. But I think in many cases, you can also get a vibe if there is any real stress on a relationship or not.
The saying goes, "The proof is in the puddin'!" Look at the families around you for help in deciding what theory produces the flavor you want. Once you have chosen, press forward with confidence.