Just curious, as an industry outsider -- what do MBB do that make them Tier 1? My experience is the Tier 2 vendors you've listed are more tactical, and typical

Just curious, as an industry outsider -- what do MBB do that make them Tier 1? My experience is the Tier 2 vendors you've listed are more tactical, and typically handle execution (outsourcing etc.). Whereas MBB are more strategic, C-Suite, but the value-add may or may not be significantly different from the former.