My instinct answer and personal bias is for Merck. The main reason is company size, global footprint and brand. That said things that can change my initial bias: role at which are you joining (the more junior the more I side with Merck), size of the team (the larger the team the more I side with Beiersdorf), your interest in international opportunities (the more interested the more I side with Merck).
I agree that internal consulting has clout and direct decision making power however that is a very important skill to learn (how to lead through influence) because that is how you will manage most things when you will be in a senior position.
hope it helps,