I'd like to complement the perspectives from another regions: Asia Pacific and Middle East.
Looking at the Asia Pacific region, AT Kearney has a much stronger presence to Roland Berger. In some countries, AT Kearney was even the first mover and had dominated the market before MBB comes in and started dividing up the pie.
In the Middle East region, mainly Dubai, AT Kearney also has an established footprint compared to Roland Berger and even Bain & Company.
Answering your inquiries regarding the 3 consideration factors:
- Future career opportunities: There are 2 factors that influence this:
(1) Exposure towards specific industries and functions within the firms. Opportunities to get involved in emerging topics such as digitalization, fintech, Industry 4.0, etc (depending on your areas of interests) will put you in a good shape for your next endeavor.
(2) Brands. This will varied across regions, e.g. In Europe, especially Germany, Roland Berger eclipsed AT Kearney. Hence, it's important to determine this aspect while taking into account your specific location / office preferences as well as the potential exposure towards industries and functions in the area.
- Entrepreneurial spirit:
Typically, the firm with smaller footprints and presence in a region presents higher opportunities for entrepreneurship, allowing one to shine and participate in different initiatives, even building up practices and offices, as opposed to a more established ones.
All said though, consulting firms generally highly encourage consultants to be actively involved in coming up with new initiatives as it will positively impact the business.
- Sustainability competencies
I can speak only for Asia Pacific region on this. Roland Berger has exposure towards a variety of projects within the sector such as aquaculture, while AT Kearney's focus mainly lies in conventional industry with operations focus such as oil & gas as well as manufacturing.
From industrial perspective, Roland Berger will have an edge in sustainability sector in Asia.
However, that is not to say that there are sustainability-focused projects and initiatives even within conventional industries that AT Kearney serves.
Hope it helps!