There are three major factors that determine whether loan applicants with poor credit can profit by shopping. The first is the size of the loan they are looking for. Brokers make most of their money by charging points, which are expressed as a percent of the loan amount. Since brokers can make more on large loans, they are more willing to compete to get the loan, and to struggle with lenders to gain an approval. The second factor is just how bad the applicant's credit is.
Many people have expectations about their credit that are way off base.
I had a letter from a consumer recently who dreaded getting a credit report because three years earlier she was late one time in paying a gas bill. In contrast to her expectations, her rating was very high. It works the other way too. Many consumers harbor the notion that their late payments haven't hurt them because they paid eventually, which is not the case. You can get at least a rough idea of how good or bad your credit is from several internet sites that provide this as a free feature.