Hi there,

As a former Principal (on the 30's), I think I can provide a good answer. It is a bit detailed, but please note this depends on the specific firm, and also on whether we are talking on MBB/Tier2 vs. Big4/Management Consulting.

Principals:

• Significant industry experience
• Strong client management skills, including at C-Level. 
• Manage the client's sponsor
• Responsibility for any kind of project, regardless of size and complexity
• Coordinate multiple teams / projects 
• Plan the whole project methodology
• Performs quality check on the overall “answer” / recommendation
• May have commercial responsibilities

Project Managers:

• Some industry experience, but usually a generalist starting to specialize
• Good client management skills, but focused on the client operational team 
• Manage the client's project team leader (hands-on counterpart, not a decision maker)
• Manage a single project with 2-4 work streams
• Coordinate a team / project at a time
• Turn the project methodology into the day to day plan
• Manages day to day work, and performs quality check on the analysis
• Usually doesn't have commercial responsibilities

Analysts:

• Generalists
• Client counterparts are more junior/operational
• Manage a workstream, may support junior analysist
• Responsible for providing zero-defect client ready analysis
• Execute the methodology
• No explicit commercial responsibilities
   

Hope this helps.