How to Evaluate a Service Bureau

Software
How well does the company code records and catch dupes? Does it outsource any services to other vendors? How do these processes affect timing, postage discounts and response rates?

Flexibility of the Merge
Can the bureau suppress using various levels of matching logic? Can it change list priorities without having to rework the input into the merge? Can the service bureau retain records with contact names over those without, regardless of their priority in the merge (that is, in a business-to-business merge)?