My experience of D&B has been generally rather bad I'm afraid. This may be because of the size of the projects with which we are concerned. With a substantial project, a D&B company has many locations in which to hide excess profits. You simply can't compare apples with apples in a tender situation with this so the competition element is removed as far as costs are concerned. An uninformed client will therefore be unable to identify if and where he or she is getting fleeced. D&B companies generally don't like pricing against someone else's design because they know that each item in the bills will be subject to the full glare of open comparison with their competitors. This assumes of course that the designer has provided a comprehensive BoQ with their tender pack. Relying on statements such as 'we only ever do good work' or 'our reputation goes before us' cuts little ice for example with government organisations required to approach procurement according to strict tendering procedure.
I think this is a major problem in our particular market place in the area of artificial sports pitch installation. So
few people know about these things that D&B installers can achieve huge profits simply because nobody knows how to compare their methods and materials with those of other companies. Thus independent design is essential in order to achieve both the desired quality and the best price.
And that's why we've been studying hard the subject of artificial sports surface construction methods and materials!