From my experience the "company auditors" tend to act with little interest in their customers as they have an employement contract and thus they are less effected by "customer satisfaction", contractors are more dependent on positive feedback to receive more work.
Howard, as always, you have very good points. The assertion quoted above is shared by many contract auditors in the industry. However, things are not so "black and white". Indeed, full time auditors are less susceptible to lose their income if one registrant blackballs him/her. However, in this very competitive market place, an auditor that is consistently and chronically rejected by clients will not remain employed very long.
When one digs at this issue, you will face one of the fundamental conundrums of this service: Having to "please" the invoice-paying customers, while maintaining the integrity of the audit and certification processes. Because, as I am tired of reminding people, the REAL users of the certificates are NOT the direct-customers of the CB's, but other stakeholders, primarily, the registrant's customers.
Some auditors, in their attempt to please the customers (registrants), allow for non-conformities to go unreported. They allow substandard systems to attain and maintain certification; doing so, they bring the whole certification process into disrepute and undermine the confidence in the value of management system certificates.
While many contract auditors work for only one or two CB's, there are some that work for a handful of registrars. For these, we have a problem because they never really learn each CB's protocol they represent.
As I mentioned several times also, most registrants are oblivious to the business models of different certification bodies and how that affects them (the registrants). Some CB's have "just-in-time", "auditor-on-demand" contract auditors all over the place, but they provide no training, no guidance to such subcontractors. The end result to the registrants? A revolving door of auditors, inconsistency of interpretation amongst auditors, different levels of customer service, etc...
By the way, with the upcoming deployment of ISO 17021:2011, the bar for competence establishment will move up. Let's see how that translates in the real world.