At the risk of being re-labeled a "snob"...
There are tiers even within "top-tier" MC firms...just like there are tiers within the "top-tier" B-schools. For example, no one would consider Michigan, Virginia (Darden), and Dartmouth (Tuck) to be in the same league as Harvard, Stanford, or Wharton...even though all these B-schools are considered "Top 10" in the US (and top-tier MCs and IBs do recruit all the top 10 schools).
Similarly, McK/B/BCG are probably considered the highest tier in MC (although McK arguably is still slightly more prestigious than the Bs). BAH have recently lost a lot of their lustre...to issues that cannot be simply explained in this thread. But agree with Tony that for all intents and purposes, BAH is still considered a top-tier firm.
The true test of prestige in this industry is -- if you were accepted to Harvard, would you enroll at Michigan? If you were hired by McK, would you still go to one of the 3 Bs? Of course, there are always exceptions (in a previous thread, I mentioned that a classmate of mine rejected an offer from McK to go to Bain)...but most would answer 'No'.