There's something to be said about getting an outside opinion on radical or long term business decisions.
As a disclaimer, I've done IT consulting (solution engineering) since leaving AA, all of it for companies outside the US. The cookie cutter consultants who always recommend the same thing are indeed useless (i.e. BCG, Landor). So are the ones who hire a bunch of kids barely old enough to rent a car by themselves, and/or no real world experience to rely on (which is what it sounds like you were dealing with).
On almost every engagement I've been on in the past three years, there are competent people employed by the client who are capable of coming up with the same recommendations we eventually do. Sometimes it's just a matter of them not knowing how to build or sell their business case. Other times, the decision makers don't buy the arguments out of sheer ignorance/incompetence, or more often, out of politics, and need to hear it confirmed (or shot down) by an outsider.
If we can show what other clients experienced when following a similar path the client wants to go down, there's a much different level of credibility to given the story, expecially when they're making a strategic mistake.
There's also the fact I can get in front of a CIO or VP and say "that's a really stupid idea, sir" without any fear of retribution. Internal guys usually don't have that level of confidence, especially when you're dealing with companies in the Middle East or Asia.
