Do physics! Especially if your main reason for wanting biology is that it would help with medicine/pharmacy, because biol isn't just the human body, it's also plants, ecosystems, animals, all sorts of things... If you're interested in maths, then I so recommend physics (yes I am on a huge physics high at the moment...I love it so much right now...
). Someone else said it, that everything in physics leads on to another and everything interrelates, while biol is just memorising *really* long names and yeah... (yes I am on a huge biology low at the moment...man I hate plant physiology!)
So yeah, there's my slightly biased opinion...