I think it depends on where you see yourself long-term. In Germany, Roland Berger seems to be slightly more prestigious than Bain and I've heard that exit options are better (Source: Brand Eins Consulting overview 2018). Should you want to move out of Germany, however, Bain would probably be better. I've also heard that they at least try to have a good work-life balance, which might be relevant if you have a partner or even children.
You said you liked the people at Roland Berger, and I would strongly recommend including that in your considerations. After all, you will spend a lot of time with your colleagues.