Pros
The people in the Midwest office of Stepping Stones Group will advocate for you and make sure you have the tools for success. This is the employer you want especially during the uncertain times with COVID-19. (I have also interacted with other staff members from other administrative SSG offices, and they are incredibly positive and encouraging.)
Even as a part-time employee, I got benefits such as a wellness stipend and professional development funds. I only left SSG for a postdoctoral research opportunity, and the professional development support I was offered for postdocs was either equal or less than the support I received from SSG.
SSG is a W-2 employer. Many contract companies use 1099's, which make your paycheck look great initially and then you have an income tax headache when filing taxes.
As a contract speech pathologist, you can focus on service delivery and the associated paperwork. In my district, if you're hired directed by the board of education, you will have to fit in extra duties (e.g. lunchroom monitor, dismissal service).
I am confident that SSG did everything they possibly could to make sure I was content as their employee. Another benefit of contracting, is that if you move, they can help you find a new placement. You could stay with SSG and explore a new geographic region.
Cons
The one con I can think of is barely a con because of all the benefits that come with being a SSG employee. The hourly rate tends to be in the mid to high-mid range when comparing to other companies. However, SSG did a lot of legwork to make sure I was still getting some pay while my district shut down. I would prefer to have an employer that pays me a slightly above average SLP wage even when times are tough than to have a high SLP wage only when times are great. A consistent paycheck that is a fair wage is much better in my opinion.