Pros
I can think of none
Cons
I had one assignment with AMS. I found them to be thoroughly unethical and predatory. If you work for them, understand that they will make a LOT of money from your labor and provide nothing in return. If you care at all about the non-profit organizations that AMS serves, understand that their only mission is to exploit those nonprofits while paying you as little as possible and providing no service to you or the nonprofit. They have no conscience and absolutely no sense of human decency. Also know that within the non-profit community, AMS has a terrible reputation. I've heard two separate people, completely independently, describe the head of their non-profit division as "smarmy". Literally- two separate people used that word to describe him.