Just randomly saw this chat and want to add an opinion on that (as Ex-McKinsey EM)…
First of all, please do not compare “prestige” with “profitability” - these times are slowly fading away when you hire a consultant based on the pure reputation. Things like, region, sector, function coverage are by far more relevant when it comes to these descisions. And especially, at times like now, probably fees matter the most (restructuring projects are sold with a heavy discount). Overall, I think the observation that McKinsey is building up more support services and “sub-entities” (Lumics, Orphos, etc.) which charge lower fees but also pay less to the consultants (hence lower Rev/FTE). But this is part of the overall strategy to grow - nowadays the clients can often do their own strategy and need rather a review or Benchmark (oh how I cannot hear this word anymore) - hence you need to create additional value add. McKinsey was always known for sending “young, unexperienced graduates” to clients by saying that they have smart people who will understand the problem fast, even if they have never done a similar project before. This business case worked in the past but gets more and more crushed by ex-consultants being clients now. To fight against it, McKinsey pushed towards implementation. BCG and Bain on the other hand were alsways far more “functional”-focussed firms (esp. Bain with their Commercial DD/PEPI focus), there you train the people to focus on sectors and functions to generate more value-add. As a result they don't need to dilute their revenue as much. Haven't looked at the number, but I would expect that Bain has even the highest margin of all of them. But what matters the most: For anybody up to Associate Partner/Principal these things don't matter much, as pay won't be significant different. The big difference comes for Partners or esp. Senior Partners, who “feel” the different profitability (here I know based on more than a handfull of Senior Partner pay-ranges that Bain Senior Partners earn 1.5-2 times more than a McKinsey ones). But again - likelyhood to stay up until that role and get elected is quite low, hence irrelevant.
On the prestige thing again - McKinsey lost on this point continuously given their strong focus on the public sector and as a result being focus of media. But still, if it comes to career opportunities post-consulting, I would frame it this way:
Go for McK, if you want to go for a typical corporate role afterwards. McK has the best network, which will help you to be directly recognized within every corporate.
Go for BCG, if you are rather a startup/bizdev person, as BCG people tend to focus on building their own business/being a bit more out of the box if it comes towards long-term career goals.
Go for Bain, if you are into Finance or esp. Private Equity Exits. Their platform, toolkit, infrastructure is by far the best and gives you the best training as well as network to make an Exit into this direction.
So, lot's of words - but hope this gives you a better view on this topics.