Pluspunten
RR is a small agency but is really trying to do things right and build for scale. Working on putting clients first without ruining the work/life balance of employees. They've seen how large companies somehow will manage to both put the client and the employee last and RR wants to do things better. Top leadership really has their heads on straight. Z&K are humble, down to earth, and are just trying to build a really great organization.
Minpunten
I think the Cons are the same as any smaller sized operation. What you're doing really matters - that means the stakes are high. Large well established companies can afford to have a person make some pretty bid mistakes, not really the case in a small organization everyone really has to carry their weight and pull in the same direction.