Pros
Good foot in the door to the industry, since the company is a big corporation and all that entails.
Cons
Firstly, management is non-existent, in a literal sense. As a Contract RA you don't speak with Biogen management directly, but rather to a proxy contract recruiting organization. They also pay you, so make sure to button up the details of your pay when you start, and if you believe you have something more to offer than you're worth, Biogen may be desperate enough to negotiate for that. The team you're on will truly treat you the same as a salaried hire which is respectful of them. At the same time, it is difficult because you may work just as hard as full-time employees but not be compensated as well. Also, your team may not be great so being treated the same is not necessarily good. The chances are high that your manager will be very cagey about if they can offer you a full-time position, so if you end up doing good work and are there for a while it will probably be frustrating. The other con is that because you are employed in this weird zone you'll feel "siloed" in your team, in a situation where no one outside your team wants to interact with you. All this amounts to a bad employment structure, so no, I do not recommend contract work.