please find below the answers to your questions.
1) In your experience, what is the main benefit of an MBA to one's career?
Generally speaking an MBA is good for three things:
- Building a network – you could easily get in touch with people who attended the same MBA in the past
- Allow to switch career – after an MBA you will be qualified for industries not available before
- Business knowledge – the actual classes you will take
The most useful long-term is usually the network. An MBA gives also credibility for a corporate career.
2) When would you recommend doing an MBA? Two years in, four years in? If a firm is sponsoring your MBA, when's the best time to do it to jump position-wise upon your return (e.g. leave as an Associate, come back as an EM)?
In many consulting firms you can join an MBA program after 2-2.5 years. You may have a chance to do that also later, but usually, the sooner the better since you will have an increasing opportunity cost later on.
The standard process is that you leave as an analyst and are hired in a pre-manager position after the MBA (Associate at McKinsey, Consultant at BCG and Bain).