Pros
The small team allows you to have a wonderful connection to everyone and feels very cosy. The founders are young and are working hard to make the company a success. The culture is great: regular feedbacks, openness but also a friendly atmosphere make sure you feel welcome and at home from the start. The learning curve is enormous and allows for an immense amount of growth in a very short period of time. You can add value to every aspect you feel you like to contribute to, so there are lots of opportunities to get involved and create a difference.
Cons
Movement within the company is a little retricted due to the size, but that's basically all there is re. cons.