Pros
I have worked at a medium (150+) and a large company (700+). The lack of visibility and support from those two companies was dismal but when I started at Synthesis, I finally found a place that actually put an emphasis on teamwork and supporting each member of that team. The small company feel ensures everyone gets to know everyone else and the company is comprised of smart, driven people who love to help others learn and to provide the best service that they possibly can to their clients. People early in their career can enjoy a laid back but focused atmosphere while building experience and those later in their career can enjoy consistent and challenging projects while having the support of the company for a work/life balance. Its nice to have a culture that does not say "Do not make mistakes" but rather "Mistakes happen but we can fix it. As long as you are pushing yourself and learning". While still a small company, the expectation for growth is high and with that the opportunities for new roles/positions for employees to transition to as they move along their career path.
Cons
Visibility to almost everyone in the company. Must be able to focus on your own work with distractions/conversations going on around you.