What's the difference btw Oliver Wyman and other second tier?

You may say is a second tier firm…based on what? on size/revenue? then I agree.

OW comes from different acquisitions/mergers and since then been growing at relevant rates, though the gap vs. MBB will never be closed (in size)

OW unique proposition is the super specialization it has in specific industries and even topics within. It is able to tackle with excellence niche topics that are highly relevant in certain or accross industries (e.g., FS, TMT, Aviation, Automotive…)

As the other answer mentions, it is a highly analytical approach and also very hands-on. That is, in addition to slide decks production, we roll up our sleeves and work hand in hand with the client, implementing, operating and delivering results and impact. I can say that in the vast majority of my engagements at OW we both made the plan/strategy and the implementation with a team skillset difficult to replicate (strong expertise in the matter).

We also bring in a global staffing approach which is a great value prop for incoming consultants as well as for the clients. I've done plenty of global strategy projects where we leverage staff from accross the world and hence tons of expertise/different market inputs. the typical project is not in your home office country, rather in a different country with consultants from different parts of the world

I've found ourselves always competing with MBB at the same level, we are even more expensive in some cases due to the global approach, sometimes we lost sometime won.

My experience at OW and my way to see it, is that it is a first tier firm in terms of everything except for the size.

But this are just my two cents