Should I get the otterbox defender or commuter?

So I'm getting my first smartphone, the iPhone 4S and I really want to make sure it's protected. Several of my friends have broken theirs from drops and I really don't want that to happen. I'm a poor college student and this is a big investment for me so I want to protect it.
I'm leaning towards the defender, because its the toughest and I like the colors it comes in best. But I'm not sure if it's going to be too big and/or bulky for me. I'm girl so I can always carry it in my purse, but sometimes I like to carry just like a wristlet, so I'd like something that I can fit into my pocket even if it's a little tight.
Basically I want something that's going to protect my phone well, but I'm just a college student and I don't do anything to hardcore that's going to be too dangerous. I just want something in case I drop it or do somethign stupid. Is the defender overkill? Is the commuter enough? What do you guys think?

I work for Sprint, and I always suggest customers buy the defender series. The case is rather bulky, expecially on bigger-screen phones, but because the iphone is such a small phone, the case is not too much. The defender series (in my opinion) are the best ones out in the way of protection. I have an otterbox on my phone, and all day long I chuck it at walls and the ground to prove to customers how durrable it is.

I'm also a girl college student, and I can feel u, so I recommend u a wallet case with a waist stripe for your loved iphone 4s. I believe that it suits u best.