Pluspunten
Variety of clients, opportunity to learn new stuff working on internal projects and the company offers reimbursement on some courses and certifications. It depends on the client but usually you do have a good life balance since you are a contractor working within the client and the client pays a lot if you need to do extra hours or be on call.
Minpunten
All the cons of a consultancy company... Below market pay, almost none benefits, if you are changing clients technical interviews will happen and you may not even have time to prepare. Review process is weird, no matter how good you perform your salary in the end depends on how they negotiated your contract with the client (and they don't review your contract prior to your review). GC process has a minimum 1 year policy which in the end becomes 2 or more to start your process.