Vantaggi
I was cooperating with AE as a contractor for about a year. As the company is interacting with businesses mainly on the out-staffing basis, - it's obvious that almost all conditions, pros, cons, and perks tightly depend on the project and customer's team. For me, the most valuable features were that the company can cover all basic needs - like a laptop, nice co-working place in the city center and proactively gather feedback and improve processes (for example, I was given the new laptop once I explained the specific of my tasks to my TL and management). Aside from other things - I'd like to notice the help with my business trip (processing for a visa, flight, booking, etc). Company staff made it possible for me to save time and think about my project duties and don't worry about anything else.
Svantaggi
No cons. I left my position because of misunderstandings in the development process on the project - as I got a few Team Leads with a different vision of my duties at the same time, but no real influence on the lifecycle of my part of the project, but I guess it's just an exclusive case so things are very different on other projects.