Which iPhone should I get?

First of all, no one try and talk me out of the iPhone, because I am definitely getting one. So I have just enough money for the iPhone 4 and I love the way it looks and everything about it, but like I said, I have JUST enough for it, no more. Until today, I had my heart set on the 4, but after thinking and realizing that I will need more money to get a case (I'm a klutz and am sure to mutilate the poor phone) and it would be nice to have money left over, so now I have the dilemma of deciding between the 4 and the 3GS. Is the 4 worth the extra money, or should I stick with the 3GS?